code: def __len__(self):
      return len(self.data)
  
file_path: doctr/tests/tensorflow/test_datasets_loader_tf.py
imports: from typing import List, Tuple
  import tensorflow
  from doctr.datasets import DataLoader
label_desc: Use image node_id 2 for calling the MockDataset obj's underlying member method code with example usage: obj.__len__() and returns: len