Register graph ops absent in op_def_registry, if present in c++ registry.

  Args:
    graph_ops: set with graph op names to register.

  Raises:
    RuntimeError: if `graph_ops` contains ops that are not in either python or
      c++ registry.

def register_ops_if_needed(graph_ops):
  """Register graph ops absent in op_def_registry, if present in c++ registry.

  Args:
    graph_ops: set with graph op names to register.

  Raises:
    RuntimeError: if `graph_ops` contains ops that are not in either python or
      c++ registry.
  """
  missing_ops = graph_ops - set(op_def_registry.get_registered_ops().keys())

  if not missing_ops:
    return

  p_buffer = c_api.TF_GetAllOpList()
  cpp_op_list = op_def_pb2.OpList()
  cpp_op_list.ParseFromString(c_api.TF_GetBuffer(p_buffer))
  cpp_registry_ops = {op.name: op for op in cpp_op_list.op}

  missing_op_list = op_def_pb2.OpList()
  for missing_op in missing_ops:
    if missing_op not in cpp_registry_ops:
      logging.info(
          "Op %s is missing from both the python and C++ registry.",
          missing_op)
    else:
      missing_op_list.op.extend([cpp_registry_ops[missing_op]])
      logging.info(
          "Adding op %s from c++ registry to python registry.",
          missing_op)

  op_def_registry.register_op_list(missing_op_list)

  # Note: Only raise missing op ValueError after trying to load ops.
  # This allows the test to exercise all the calls into TensorFlow
  # without having to write a C + python test.
  if not missing_ops <= set(cpp_registry_ops.keys()):
    raise RuntimeError(
        "Graph ops missing from the python registry (%s) are also absent from "
        "the c++ registry."
        % missing_ops.difference(set(cpp_registry_ops.keys())))