message: Add support for RNN state array of type tf.identity.
diff: @@ -47,7 +47,8 @@ bool RemoveUnusedOp::Run(Model* model, std::size_t op_index) {
  bool found_output_as_rnn_state_array = false;
  for (const auto& rnn_state : model->flags.rnn_states()) {
  if (output == rnn_state.state_array()) {
  - CHECK(op->type == OperatorType::kFill);
  + CHECK(op->type == OperatorType::kFill ||
  + op->type == OperatorType::kTensorFlowIdentity);
  found_output_as_rnn_state_array = true;
  break;
  }
  