message: Update loader_impl.py
diff: @@ -167,7 +167,7 @@ def _get_main_op_tensor(
  Args:
  meta_graph_def_to_load: The meta graph def from the SavedModel to be loaded.
  - init_op_key: name of collection to check; should be one of MAIN_OP_KEY
  + init_op_key: name of the collection to check; should be one of MAIN_OP_KEY
  or the deprecated LEGACY_INIT_OP_KEY
  Returns:
  