for (auto msubgraph : *mutable_subgraphs) {
    auto operators = msubgraph->mutable_operators();
    for (auto op : *operators) {
      auto opcode_idx = op->opcode_index();
      auto opcodes = mutable_model->operator_codes();
      auto opcode = (*opcodes)[opcode_idx]->builtin_code();
      if (opcode == tflite::BuiltinOperator_CUSTOM) {
        std::vector<int32_t> inputs(op->inputs()->begin(), op->inputs()->end());

  ASSERT_THAT(GetBuiltinCode(model_.operator_codes[op1->opcode_index].get()),
              Eq(BuiltinOperator_QUANTIZE));
  ASSERT_THAT(GetBuiltinCode(model_.operator_codes[op2->opcode_index].get()),
              Eq(BuiltinOperator_QUANTIZE));
  ASSERT_THAT(GetBuiltinCode(model_.operator_codes[op3->opcode_index].get()),
              Eq(BuiltinOperator_PACK));

      const auto op = subgraph->operators()->Get(op_idx);
      for (size_t i = 0; i < op->outputs()->size(); ++i) {
        if (op->outputs()->Get(i) == tensor_idx) {
          const uint32_t op_code_idx = op->opcode_index();
          *op_code = GetBuiltinCode(model->operator_codes()->Get(op_code_idx));
          return true;
        }
      }
    }
    return false;
  }
};