code: def test_create_a_python_data_source():
      source = python.PythonDataSource(length=2, getitem=getitem)
      assert len(source) == 2
      assert source[0] == 0
      assert source[1] == 1
      assert source[2] == 2
  
file_path: datasets/tensorflow_datasets/core/data_sources/python_test.py
imports: import pickle
  from unittest import mock
  from tensorflow_datasets.core.data_sources import python
  import tree
label_desc: Use image node_id 2 for calling a global function with example usage: test_create_a_python_data_source() without return types