tf.keras.layers.Concatenate() works with a list but fails on a tuple of tensors - tensorflow

Question

This will work:
tf.keras.layers.Concatenate()([features['a'], features['b']])
While this:
tf.keras.layers.Concatenate()((features['a'], features['b']))
Results in:
TypeError: int() argument must be a string or a number, not 'TensorShapeV1'
Is that expected? If so - why does it matter what sequence do I pass?
Thanks,
Zach
EDIT (adding a code example):
import pandas as pd
import numpy as np
data = {
'a': [1.0, 2.0, 3.0],
'b': [0.1, 0.3, 0.2],
}
with tf.Session() as sess:
ds = tf.data.Dataset.from_tensor_slices(data)
ds = ds.batch(1)
it = ds.make_one_shot_iterator()
features = it.get_next()
concat = tf.keras.layers.Concatenate()((features['a'], features['b']))
try:
while True:
print(sess.run(concat))
except tf.errors.OutOfRangeError:
pass
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-135-0e1a45017941> in <module>()
6 features = it.get_next()
7
----> 8 concat = tf.keras.layers.Concatenate()((features['a'], features['b']))
9
10
google3/third_party/tensorflow/python/keras/engine/base_layer.py in __call__(self, inputs, *args, **kwargs)
751 # the user has manually overwritten the build method do we need to
752 # build it.
--> 753 self.build(input_shapes)
754 # We must set self.built since user defined build functions are not
755 # constrained to set self.built.
google3/third_party/tensorflow/python/keras/utils/tf_utils.py in wrapper(instance, input_shape)
148 tuple(tensor_shape.TensorShape(x).as_list()) for x in input_shape]
149 else:
--> 150 input_shape = tuple(tensor_shape.TensorShape(input_shape).as_list())
151 output_shape = fn(instance, input_shape)
152 if output_shape is not None:
google3/third_party/tensorflow/python/framework/tensor_shape.py in __init__(self, dims)
688 else:
689 # Got a list of dimensions
--> 690 self._dims = [as_dimension(d) for d in dims_iter]
691
692 #property
google3/third_party/tensorflow/python/framework/tensor_shape.py in as_dimension(value)
630 return value
631 else:
--> 632 return Dimension(value)
633
634
google3/third_party/tensorflow/python/framework/tensor_shape.py in __init__(self, value)
183 raise TypeError("Cannot convert %s to Dimension" % value)
184 else:
--> 185 self._value = int(value)
186 if (not isinstance(value, compat.bytes_or_text_types) and
187 self._value != value):
TypeError: int() argument must be a string or a number, not 'TensorShapeV1'

Answer 1

https://github.com/keras-team/keras/blob/master/keras/layers/merge.py#L329
comment on the concanate class states it requires a list.
this class calls K.backend's concatenate function
https://github.com/keras-team/keras/blob/master/keras/backend/tensorflow_backend.py#L2041
which also states it requires a list.
in tensorflow https://github.com/tensorflow/tensorflow/blob/r1.12/tensorflow/python/ops/array_ops.py#L1034
also states it requires a list of tensors. Why? I don't know. in this function the tensors (variable called "values") actually gets checked if its a list or tuple. but somewhere along the way you still get an error.