ArgView output_arg = op_.OnlyOutput();
  Statement("int num_retvals = $0.size()", output_arg.VariableName());
  Statement("return " + Call(op_.VariableName(), "Execute",
                             {output_arg.VariableName(), "&num_retvals"}));
}

void OpImplementationRenderer::RenderExecutionSingleOutput() {
  ArgView output_arg = op_.OnlyOutput();
  Statement("int num_retvals = 1");

int OpView::NumOutputs() const { return output_args_.size(); }

ArgView OpView::OnlyInput() const {
  CHECK_EQ(input_args_.size(), 1);  // Crash OK
  return input_args_.front();
}

ArgView OpView::OnlyOutput() const {
  CHECK_EQ(output_args_.size(), 1);  // Crash OK
  return output_args_.front();
}

string OpView::FunctionName() const { return op_.name(); }

  const std::vector<AttrView> &Attributes() const;
  const std::vector<OpArgumentView> &AllArguments() const;

  int NumInputs() const;
  int NumOutputs() const;
  ArgView OnlyInput() const;
  ArgView OnlyOutput() const;

  string FunctionName() const;
  string VariableName() const;
  string OpNameString() const;
  string Summary() const;
  std::vector<string> Description() const;
  bool IsListOp() const;

 private: