class_docstr: Test the hint to stub functionality.
class_docstr_tok: ["Test","the","hint","to","stub","functionality","."]
code: def _get_input_index(self, x):
      return x.op.node_def.attr[
          op_hint.OpHint.FUNCTION_INPUT_INDEX_ATTR
      ].i
  
imports: from unittest import mock
  import numpy
  from tensorflow.lite.python import convert
  from tensorflow.lite.python import op_hint
  from tensorflow.lite.python.interpreter import Interpreter
  from tensorflow.lite.python.metrics import converter_error_data_pb2
  from tensorflow.lite.python.metrics.wrapper import metrics_wrapper
  from tensorflow.lite.toco import toco_flags_pb2
  from tensorflow.python.client import session
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import test_util
  from tensorflow.python.framework.graph_util_impl import _bfs_for_reachable_nodes
  from tensorflow.python.framework.graph_util_impl import _extract_graph_summary
  from tensorflow.python.framework.graph_util_impl import _node_name
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import array_ops_stack
  from tensorflow.python.ops import math_ops
  from tensorflow.python.platform import test
label_desc: Use image node_id 6 for calling the ConvertTestOpHint obj's underlying member method code with example usage: obj._get_input_index(x) and returns: x