code: def __getitem__(self, key):
      return key
  
file_path: nnabla/python/test/test_indexing.py
imports: import pytest
  import numpy
  import nnabla
  from nnabla.testing import assert_allclose
label_desc: Use image node_id 1 for calling the Key2Key obj's underlying member method code with example usage: obj.__getitem__(key) and returns: key