Tensorboard callback doesn't work when calling - tensorflow

I am new to Tensorflow and Keras. I just started beginning my Deep learning Journey. I installed Tensorflow 2.4.3 as well as Keras. I was learning Tensorboard. I created a model for imdb dataset as follows
import tensorflow as tf
import keras
from tensorflow.keras import *
from tensorflow.keras.datasets import imdb
from tensorflow.keras.preprocessing import sequence
## model making
max_features = 2000
max_len = 500
(x_train, y_train), (x_test, y_test) = imdb.load_data(num_words=max_features)
x_train = sequence.pad_sequences(x_train, maxlen=max_len)
x_test = sequence.pad_sequences(x_test, maxlen=max_len)
model = models.Sequential()
model.add(layers.Embedding(max_features, 128,
input_length=max_len,
name='embed'))
model.add(layers.Conv1D(32, 7, activation='relu'))
model.add(layers.MaxPooling1D(5))
model.add(layers.Conv1D(32, 7, activation='relu'))
model.add(layers.GlobalMaxPooling1D())
model.add(layers.Dense(1))
model.summary()
model.compile(optimizer='rmsprop',
loss='binary_crossentropy',
metrics=['acc'])
I used the tensorboard callback here.
callbacks = [
keras.callbacks.TensorBoard(
log_dir='my_log_dir',
histogram_freq=1,
embeddings_freq=1,
)
]
history = model.fit(x_train, y_train,
epochs=3,
batch_size=128,
validation_split=0.2,
callbacks=callbacks)
Then I got the following warning.
C:\Users\ktripat\Anaconda3\envs\tf2\lib\site-packages\keras\callbacks\tensorboard_v2.py:102: UserWarning: The TensorBoard callback does not support embeddings display when using TensorFlow 2.0. Embeddings-related arguments are ignored.
warnings.warn('The TensorBoard callback does not support.'
Please find any solution if you guys have any. Thank you in advance!

You will need to follow this guide.
It describes how to save the weights of your embedding layer in a way that you can visualize it in TensorBoard:
# Set up a logs directory, so Tensorboard knows where to look for files.
log_dir='/logs/imdb-example/'
if not os.path.exists(log_dir):
os.makedirs(log_dir)
# Save Labels separately on a line-by-line manner.
with open(os.path.join(log_dir, 'metadata.tsv'), "w") as f:
for subwords in encoder.subwords:
f.write("{}\n".format(subwords))
# Fill in the rest of the labels with "unknown".
for unknown in range(1, encoder.vocab_size - len(encoder.subwords)):
f.write("unknown #{}\n".format(unknown))
# Save the weights we want to analyze as a variable. Note that the first
# value represents any unknown word, which is not in the metadata, here
# we will remove this value.
weights = tf.Variable(model.layers[0].get_weights()[0][1:])
# Create a checkpoint from embedding, the filename and key are the
# name of the tensor.
checkpoint = tf.train.Checkpoint(embedding=weights)
checkpoint.save(os.path.join(log_dir, "embedding.ckpt"))
# Set up config.
config = projector.ProjectorConfig()
embedding = config.embeddings.add()
# The name of the tensor will be suffixed by `/.ATTRIBUTES/VARIABLE_VALUE`.
embedding.tensor_name = "embedding/.ATTRIBUTES/VARIABLE_VALUE"
embedding.metadata_path = 'metadata.tsv'
projector.visualize_embeddings(log_dir, config)
If you want to visualize during training, you can call this code in a save callback during training every X episodes using this.

Related

How to unfold Xception layers in TensorFlow

I am following the official Keras transfer learning and fine-tuning tutorial. It consists of loading the Xception model with include_top=False, and adding a new classifier part on top.
I am then saving the model with model.save() and loading with load_model().
So this is what I see when I do model.summary()
My problem is that I would like to iterate through the layers, while now Xception layers are somehow folded (on the picture: xception(Functional)). Is there a way to somehow unfold it, to see all the layers (including those that are creating Xception)?
For model. summary(), you can unfold that as follows:
from tensorflow import keras
base_model = keras.applications.Xception(
weights='imagenet', # Load weights pre-trained on ImageNet.
input_shape=(150, 150, 3),
include_top=False) # Do not include the ImageNet classifier at the top.
inputs = keras.Input(shape=(150, 150, 3))
x = base_model(inputs, training=False)
x = keras.layers.GlobalAveragePooling2D()(x)
outputs = keras.layers.Dense(1)(x)
model = keras.Model(inputs, outputs)
model.summary() # full model
model.layers[1].summary() # only xception model
Note, you cal also see the layer using the plot_model utility.
keras.utils.plot_model(model, expand_nested=True)

degraded accuracy performance with overfitting when downgrading from tensorflow 2.3.1 to tensorflow 1.14 or 1.15 on multiclass categorization

I made a script in tensorflow 2.x but I had to downconvert it to tensorflow 1.x (tested in 1.14 and 1.15). However, the tf1 version performs very differently (10% accuracy lower on the test set). See also the plot for train and validation performance (diagram is attached below).
Looking at the operations needed for the migration from tf1 to tf2 it seems that only the Adam learning rate may be a problem but I'm defining it explicitly tensorflow migration
I've reproduced the same behavior both locally on GPU and CPU and on colab. The keras used was the one built-in in tensorflow (tf.keras). I've used the following functions (both for train,validation and test), using a sparse categorization (integers):
train_datagen = tf.keras.preprocessing.image.ImageDataGenerator(
horizontal_flip=horizontal_flip,
#rescale=None, #not needed for resnet50
preprocessing_function=None,
validation_split=None)
train_dataset = train_datagen.flow_from_directory(
directory=train_dir,
target_size=image_size,
class_mode='sparse',
batch_size=batch_size,
shuffle=True)
And the model is a simple resnet50 with a new layer on top:
IMG_SHAPE = img_size+(3,)
inputs = Input(shape=IMG_SHAPE, name='image_input',dtype = tf.uint8)
x = tf.cast(inputs, tf.float32)
# not working in this version of keras. inserted in imageGenerator
x = preprocess_input_resnet50(x)
base_model = tf.keras.applications.ResNet50(
include_top=False,
input_shape = IMG_SHAPE,
pooling=None,
weights='imagenet')
# Freeze the pretrained weights
base_model.trainable = False
x=base_model(x)
# Rebuild top
x = GlobalAveragePooling2D(data_format='channels_last',name="avg_pool")(x)
top_dropout_rate = 0.2
x = Dropout(top_dropout_rate, name="top_dropout")(x)
outputs = Dense(num_classes,activation="softmax", name="pred_out")(x)
model = Model(inputs=inputs, outputs=outputs,name="ResNet50_comp")
optimizer = tf.keras.optimizers.Adam(lr=learning_rate)
model.compile(optimizer=optimizer,
loss="sparse_categorical_crossentropy",
metrics=['accuracy'])
And then I'm calling the fit function:
history = model.fit_generator(train_dataset,
steps_per_epoch=n_train_batches,
validation_data=validation_dataset,
validation_steps=n_val_batches,
epochs=initial_epochs,
verbose=1,
callbacks=[stopping])
I've reproduced the same behavior for example with the following full script (applied to my dataset and changed to adam and removed intermediate final dense layer):
deep learning sandbox
The easiest way to replicate this behavior was to enable or disable the following line on a tf2 environment with the same script and add the following line to it. However, I've tested also on tf1 environments (1.14 and 1.15):
tf.compat.v1.disable_v2_behavior()
Sadly I cannot provide the dataset.
Update 26/11/2020
For full reproducibility I've obtained a similar behaviour by means of the food101 (101 categories) dataset enabling tf1 behaviour with 'tf.compat.v1.disable_v2_behavior()'. The following is the script executed with tensorflow-gpu 2.2.0:
#%% ref https://medium.com/deeplearningsandbox/how-to-use-transfer-learning-and-fine-tuning-in-keras-and-tensorflow-to-build-an-image-recognition-94b0b02444f2
import os
import sys
import glob
import argparse
import matplotlib.pyplot as plt
import tensorflow as tf
# enable and disable this to obtain tf1 behaviour
tf.compat.v1.disable_v2_behavior()
from tensorflow.keras import __version__
from tensorflow.keras.applications.resnet50 import ResNet50, preprocess_input
from tensorflow.keras.models import Model
from tensorflow.keras.layers import Dense, GlobalAveragePooling2D
from tensorflow.keras.optimizers import Adam
# since i'm using resnet50 weights from imagenet, i'm using food101 for
# similar but different categorization tasks
# pip install tensorflow-datasets if tensorflow_dataset not found
import tensorflow_datasets as tfds
(train_ds,validation_ds),info= tfds.load('food101', split=['train','validation'], shuffle_files=True, with_info=True)
assert isinstance(train_ds, tf.data.Dataset)
print(train_ds)
#%%
IM_WIDTH, IM_HEIGHT = 224, 224
NB_EPOCHS = 10
BAT_SIZE = 32
def get_nb_files(directory):
"""Get number of files by searching directory recursively"""
if not os.path.exists(directory):
return 0
cnt = 0
for r, dirs, files in os.walk(directory):
for dr in dirs:
cnt += len(glob.glob(os.path.join(r, dr + "/*")))
return cnt
def setup_to_transfer_learn(model, base_model):
"""Freeze all layers and compile the model"""
for layer in base_model.layers:
layer.trainable = False
model.compile(optimizer='rmsprop', loss='sparse_categorical_crossentropy', metrics=['accuracy'])
def add_new_last_layer(base_model, nb_classes):
"""Add last layer to the convnet
Args:
base_model: keras model excluding top
nb_classes: # of classes
Returns:
new keras model with last layer
"""
x = base_model.output
x = GlobalAveragePooling2D()(x)
#x = Dense(FC_SIZE, activation='relu')(x) #new FC layer, random init
predictions = Dense(nb_classes, activation='softmax')(x) #new softmax layer
model = Model(inputs=base_model.input, outputs=predictions)
return model
def train(nb_epoch, batch_size):
"""Use transfer learning and fine-tuning to train a network on a new dataset"""
#nb_train_samples = train_ds.cardinality().numpy()
nb_train_samples=info.splits['train'].num_examples
nb_classes = info.features['label'].num_classes
classes_names = info.features['label'].names
#nb_val_samples = validation_ds.cardinality().numpy()
nb_val_samples = info.splits['validation'].num_examples
#nb_epoch = int(args.nb_epoch)
#batch_size = int(args.batch_size)
def preprocess(features):
#print(features['image'], features['label'])
image = tf.image.resize(features['image'], [224,224])
#image = tf.divide(image, 255)
#print(image)
# data augmentation
image=tf.image.random_flip_left_right(image)
image = preprocess_input(image)
label = features['label']
# for categorical crossentropy
#label = tf.one_hot(label,101,axis=-1)
#return image, tf.cast(label, tf.float32)
return image, label
#pre-processing the dataset to fit a specific image size and 2D labelling
train_generator = train_ds.map(preprocess).batch(batch_size).repeat()
validation_generator = validation_ds.map(preprocess).batch(batch_size).repeat()
#train_generator=train_ds
#validation_generator=validation_ds
#fig = tfds.show_examples(validation_generator, info)
# setup model
base_model = ResNet50(weights='imagenet', include_top=False) #include_top=False excludes final FC layer
model = add_new_last_layer(base_model, nb_classes)
# transfer learning
setup_to_transfer_learn(model, base_model)
history = model.fit(
train_generator,
epochs=nb_epoch,
steps_per_epoch=nb_train_samples//BAT_SIZE,
validation_data=validation_generator,
validation_steps=nb_val_samples//BAT_SIZE)
#class_weight='auto')
#execute
history = train(nb_epoch=NB_EPOCHS, batch_size=BAT_SIZE)
And the performance on food101 dataset:
update 27/11/2020
It's possible to see the discrepancy also in the way smaller oxford_flowers102 dataset:
(train_ds,validation_ds,test_ds),info= tfds.load('oxford_flowers102', split=['train','validation','test'], shuffle_files=True, with_info=True)
Nb: the above plot shows confidences given by running the same training multiple times and evaluatind mean and std to check for the effects on random weights initialization and data augmentation.
Moreover I've tried some hyperparameter tuning on tf2 resulting in the following picture:
changing optimizer (adam and rmsprop)
not applying horizontal flipping aumgentation
deactivating keras resnet50 preprocess_input
Thanks in advance for every suggestion. Here are the accuracy and validation performance on tf1 and tf2 on my dataset:
Update 14/12/2020
I'm sharing the colab for reproducibility on oxford_flowers at the clic of a button:
colab script
I came across something similar, when doing the opposite migration (from TF1+Keras to TF2).
Running this code below:
# using TF2
import numpy as np
from tensorflow.keras.applications.resnet50 import ResNet50
fe = ResNet50(include_top=False, pooling="avg")
out = fe.predict(np.ones((1,224,224,3))).flatten()
sum(out)
>>> 212.3205274187726
# using TF1+Keras
import numpy as np
from keras.applications.resnet50 import ResNet50
fe = ResNet50(include_top=False, pooling="avg")
out = fe.predict(np.ones((1,224,224,3))).flatten()
sum(out)
>>> 187.23898954353717
you can see the same model from the same library on different versions does not return the same value (using sum as a quick check-up). I found the answer to this mysterious behavior in this other SO answer: ResNet model in keras and tf.keras give different output for the same image
Another recommendation I'd give you is, try using pooling from inside applications.resnet50.ResNet50 class, instead of the additional layer in your function, for simplicity, and to remove possible problem-generators :)

Keras ValueError trying to load model

I am using Anaconda Navigator, Jupyter to be precised.
import tensorflow as tf
from tensorflow import keras
print(tf.__version__)
>>> 1.14.0
This is my model
def create_model():
model = tf.keras.Sequential([
keras.layers.Dense(86, activation='relu', kernel_regularizer=keras.regularizers.l2(0.0001),input_shape=(129,)),
keras.layers.Dropout(0.2),
keras.layers.Dense(142, activation='relu', kernel_regularizer=keras.regularizers.l2(0.0001)),
keras.layers.Dropout(0.2),
keras.layers.Dense(4, activation='softmax')
])
return model
model = create_model()
# Display the model's architecture
model.summary()
After training,predicting and evaluating my model, I decided to save it using
model.save('/Users/Jennifer/myproject/my_model.h5')
I checked the directory and folder with the h5py file. And I decided to load it using
new_model1 = tf.keras.models.load_model('/Users/Jennifer/myproject/my_model.h5')
I got an Error
ValueError: Unknown entries in loss dictionary: ['class_name', 'config']. Only expected following keys: ['dense_17']
Please help me. What should I do? I have almost spent the whole day trying to solve this issue. Thanks
Here is a bit of a work around that just loads the weights:
#!/usr/bin/env python3
from tensorflow import keras
import os
def create_model():
model = keras.Sequential([
keras.layers.Dense(86, activation='relu', kernel_regularizer=keras.regularizers.l2(0.0001),input_shape=(129,)),
keras.layers.Dropout(0.2),
keras.layers.Dense(142, activation='relu', kernel_regularizer=keras.regularizers.l2(0.0001)),
keras.layers.Dropout(0.2),
keras.layers.Dense(4, activation='softmax')
])
return model
if os.path.exists("junk.h5"):
model = create_model()
model.load_weights("junk.h5")
else:
model = create_model()
model.compile(optimizer=keras.optimizers.Adam(0.0001), loss=keras.losses.CategoricalCrossentropy(from_logits=True), metrics=['accuracy'])
model.save("junk.h5")
Another workaround would be to save the model without the optimizer
model.save("junk.h5", include_optimizer=False)
It looks like the loss function you're using creates a dictionary that has invalid keys. This sounds like a bug in keras/tensorflow. That is why the colab one probably worked because it was using a newer version.

How ensure that Keras is using GPU with tensorflow backend?

I've created virtual notebook on Paperspace cloud infrastructure with Tensorflow GPU P5000 virtual instance on the backend.
When i am starting to train my network, it woks 2x SLOWER than on my MacBook Pro with pure CPU runtime engine.
How could i ensure that Keras NN is using GPU instead of CPU during training process?
Please find my code below:
from tensorflow.contrib.keras.api.keras.models import Sequential
from tensorflow.contrib.keras.api.keras.layers import Dense
from tensorflow.contrib.keras.api.keras.layers import Dropout
from tensorflow.contrib.keras.api.keras import utils as np_utils
import numpy as np
import pandas as pd
# Read data
pddata= pd.read_csv('data/data.csv', delimiter=';')
# Helper function (prepare & test data)
def split_to_train_test (data):
trainLenght = len(data) - len(data)//10
trainData = data.loc[:trainLenght].sample(frac=1).reset_index(drop=True)
testData = data.loc[trainLenght+1:].sample(frac=1).reset_index(drop=True)
trainLabels = trainData.loc[:,"Label"].as_matrix()
testLabels = testData.loc[:,"Label"].as_matrix()
trainData = trainData.loc[:,"Feature 0":].as_matrix()
testData = testData.loc[:,"Feature 0":].as_matrix()
return (trainData, testData, trainLabels, testLabels)
# prepare train & test data
(X_train, X_test, y_train, y_test) = split_to_train_test (pddata)
# Convert labels to one-hot notation
Y_train = np_utils.to_categorical(y_train, 3)
Y_test = np_utils.to_categorical(y_test, 3)
# Define model in Keras
def create_model(init):
model = Sequential()
model.add(Dense(101, input_shape=(101,), kernel_initializer=init, activation='tanh'))
model.add(Dense(101, kernel_initializer=init, activation='tanh'))
model.add(Dense(101, kernel_initializer=init, activation='tanh'))
model.add(Dense(101, kernel_initializer=init, activation='tanh'))
model.add(Dense(3, kernel_initializer=init, activation='softmax'))
return model
# Train the model
uniform_model = create_model("glorot_normal")
uniform_model.compile(loss='categorical_crossentropy', optimizer='sgd', metrics=['accuracy'])
uniform_model.fit(X_train, Y_train, batch_size=1, epochs=300, verbose=1, validation_data=(X_test, Y_test))
You need to run your network with log_device_placement = True set in the TensorFlow session (the line before the last in the sample code below.) Interestingly enough, if you set that in a session, it will still apply when Keras does the fitting. So this code below (tested) does output the placement for each tensor. Please note, I've short-circuited the data reading because your data wan't available, so I'm just running the network with random data. The code this way is self-contained and runnable by anyone. Another note: if you run this from Jupyter Notebook, the output of the log_device_placement will go to the terminal where Jupyter Notebook was started, not the notebook cell's output.
from tensorflow.contrib.keras.api.keras.models import Sequential
from tensorflow.contrib.keras.api.keras.layers import Dense
from tensorflow.contrib.keras.api.keras.layers import Dropout
from tensorflow.contrib.keras.api.keras import utils as np_utils
import numpy as np
import pandas as pd
import tensorflow as tf
# Read data
#pddata=pd.read_csv('data/data.csv', delimiter=';')
pddata = "foobar"
# Helper function (prepare & test data)
def split_to_train_test (data):
return (
np.random.uniform( size = ( 100, 101 ) ),
np.random.uniform( size = ( 100, 101 ) ),
np.random.randint( 0, size = ( 100 ), high = 3 ),
np.random.randint( 0, size = ( 100 ), high = 3 )
)
trainLenght = len(data) - len(data)//10
trainData = data.loc[:trainLenght].sample(frac=1).reset_index(drop=True)
testData = data.loc[trainLenght+1:].sample(frac=1).reset_index(drop=True)
trainLabels = trainData.loc[:,"Label"].as_matrix()
testLabels = testData.loc[:,"Label"].as_matrix()
trainData = trainData.loc[:,"Feature 0":].as_matrix()
testData = testData.loc[:,"Feature 0":].as_matrix()
return (trainData, testData, trainLabels, testLabels)
# prepare train & test data
(X_train, X_test, y_train, y_test) = split_to_train_test (pddata)
# Convert labels to one-hot notation
Y_train = np_utils.to_categorical(y_train, 3)
Y_test = np_utils.to_categorical(y_test, 3)
# Define model in Keras
def create_model(init):
model = Sequential()
model.add(Dense(101, input_shape=(101,), kernel_initializer=init, activation='tanh'))
model.add(Dense(101, kernel_initializer=init, activation='tanh'))
model.add(Dense(101, kernel_initializer=init, activation='tanh'))
model.add(Dense(101, kernel_initializer=init, activation='tanh'))
model.add(Dense(3, kernel_initializer=init, activation='softmax'))
return model
# Train the model
uniform_model = create_model("glorot_normal")
uniform_model.compile(loss='categorical_crossentropy', optimizer='sgd', metrics=['accuracy'])
with tf.Session( config = tf.ConfigProto( log_device_placement = True ) ):
uniform_model.fit(X_train, Y_train, batch_size=1, epochs=300, verbose=1, validation_data=(X_test, Y_test))
Terminal output (partial, it was way too long):
...
VarIsInitializedOp_13: (VarIsInitializedOp): /job:localhost/replica:0/task:0/device:GPU:0
2018-04-21 21:54:33.485870: I tensorflow/core/common_runtime/placer.cc:884]
VarIsInitializedOp_13: (VarIsInitializedOp)/job:localhost/replica:0/task:0/device:GPU:0
training/SGD/mul_18/ReadVariableOp: (ReadVariableOp): /job:localhost/replica:0/task:0/device:GPU:0
2018-04-21 21:54:33.485895: I tensorflow/core/common_runtime/placer.cc:884]
training/SGD/mul_18/ReadVariableOp: (ReadVariableOp)/job:localhost/replica:0/task:0/device:GPU:0
training/SGD/Variable_9/Read/ReadVariableOp: (ReadVariableOp): /job:localhost/replica:0/task:0/device:GPU:0
2018-04-21 21:54:33.485903: I tensorflow/core/common_runtime/placer.cc:884]
training/SGD/Variable_9/Read/ReadVariableOp: (ReadVariableOp)/job:localhost/replica:0/task:0/device:GPU:0
...
Note the GPU:0 at the end of many lines.
Tensorflow manual's relevant page: Using GPU: Logging Device Placement.
Put this near the top of your jupyter notebook. Comment out what you don't need.
# confirm TensorFlow sees the GPU
from tensorflow.python.client import device_lib
assert 'GPU' in str(device_lib.list_local_devices())
# confirm Keras sees the GPU (for TensorFlow 1.X + Keras)
from keras import backend
assert len(backend.tensorflow_backend._get_available_gpus()) > 0
# confirm PyTorch sees the GPU
from torch import cuda
assert cuda.is_available()
assert cuda.device_count() > 0
print(cuda.get_device_name(cuda.current_device()))
NOTE: With the release of TensorFlow 2.0, Keras is now included as part of the TF API.
Originally answerwed here.
Considering keras is a built-in of tensorflow since version 2.0:
import tensorflow as tf
tf.test.is_built_with_cuda()
tf.test.is_gpu_available(cuda_only = True)
NOTE: the latter method may take several minutes to run.

Keras,models.add() missing 1 required positional argument: 'layer'

I'm classifying digits of the MNIST dataset using a simple feed forward neural net with Keras. So I execute the code below.
import os
import tensorflow as tf
import keras
from keras.models import Sequential
from keras.layers import Dense, Activation
from tensorflow.examples.tutorials.mnist import input_data
mnist = input_data.read_data_sets('/tmp/data', one_hot=True)
# Path to Computation graphs
LOGDIR = './graphs_3'
# start session
sess = tf.Session()
#Hyperparameters
LEARNING_RATE = 0.01
BATCH_SIZE = 1000
EPOCHS = 10
# Layers
HL_1 = 1000
HL_2 = 500
# Other Parameters
INPUT_SIZE = 28*28
N_CLASSES = 10
model = Sequential
model.add(Dense(HL_1, input_dim=(INPUT_SIZE,), activation="relu"))
#model.add(Activation(activation="relu"))
model.add(Dense(HL_2, activation="relu"))
#model.add(Activation("relu"))
model.add(Dropout(rate=0.9))
model.add(Dense(N_CLASSES, activation="softmax"))
model.compile(
optimizer="Adam",
loss="categorical_crossentropy",
metrics=['accuracy'])
# one_hot_labels = keras.utils.to_categorical(labels, num_classes=10)
model.fit(
x=mnist.train.images,
y=mnist.train.labels,
epochs=EPOCHS,
batch_size=BATCH_SIZE)
score = model.evaluate(
x=mnist.test.images,
y=mnist.test.labels)
print("score = ", score)
However, I get the following error:
model.add(Dense(1000, input_dim=(INPUT_SIZE,), activation="relu"))
TypeError: add() missing 1 required positional argument: 'layer'
The syntax is exactly as shown in the keras docs. I am using keras 2.0.9, so I don't think it's a version control problem. Did I do something wrong?
It seems perfect indeed....
But I noticed you're not creating "an instance" of a sequential model, your using the class name instead:
#yours: model = Sequential
#correct:
model = Sequential()
Since the methods in a class are always declared containing self as the first argument, calling the methods without an instance will probably require the instance as the first argument (which is self).
The method's definition is def add(self,layer,...):