tensorflow 2.8 dataset get single element error - tensorflow

Question

I would like to use "get_single_element" to get the one batch dataset as dict. The keys in dict are features names. The values are values.
My code is in tf2.8 on EC2 instance and run from jupyter.
import pandas as pd
import tensorflow as tf
df = pd.DataFrame({
'id': [1, 2, 6, 3, 5, 0],
'value_1': [10.892561, 7.210528, 1.2278101, -9.251782, 0.2118367, 6.9128551],
'value_2': ['large', 'small', 'mid','small','large', 'mid'],
'name_1': ['tyne', 'wnhp', 'ebhg','lpzhn','tyne', 'ebhg'],
'label': [0, 1, 0, 1, 1, 1]
})
dataset = tf.data.Dataset.from_tensor_slices(dict(df))
dataset = dataset.batch(2)
print(type(dataset))
print(dataset)
print(len(dataset))
class Features(object):
feature_data = {
"id": tf.io.FixedLenFeature((1,), dtype=tf.int8),
"value_1": tf.io.VarLenFeature(dtype=tf.float32),
"value_2": tf.io.FixedLenFeature((1,), dtype=tf.string),
"name_1": tf.io.FixedLenFeature((1,), dtype=tf.string)
}
label_data = {"label": tf.io.FixedLenFeature((1,), dtype=tf.int8)}
def process_sample(ds):
print(f"ds type is {type(ds)}")
features = tf.io.parse_single_example(ds, Features.feature_data) # error !
labels = tf.io.parse_single_example(ds, Features.label_data)['label']
return (features, labels)
dataset = dataset.map(lambda x: process_sample(x), num_parallel_calls=tf.data.AUTOTUNE)
dataset = tf.data.Dataset.get_single_element(dataset.batch(len(dataset)))
print(f"dataset type is {type(dataset)} dataset is {dataset}")
def get_dict(input_ds):
feature_dict_tensors = dict(input_ds)
print(f"\feature_dict_tensors type is {type(feature_dict_tensors)}, feature_dict_tensors is {feature_dict_tensors}")
return feature_dict_tensors
ds = dataset.map(get_dict)
print(f"ds type is {type(ds)}")
print(ds)
I got error:
File "<ipython-input-4-e9407f42e0a7>", line 37, in None *
lambda x: process_sample(x), num_parallel_calls=tf.data.AUTOTUNE)
File "<ipython-input-4-e9407f42e0a7>", line 33, in process_sample *
features = tf.io.parse_single_example(ds, Features.feature_data)
TypeError: Expected any non-tensor type, but got a tensor instead.
Based on https://www.tensorflow.org/api_docs/python/tf/io/parse_single_example, the first argument should be
A scalar string Tensor, a single serialized Example.
Why I got this error ?
thanks