input:                         
  def add_numbers(calculator: Calculator) -> int:
      """ Given a calculator class instance that implements the method add_two_numbers, 
      use this method to add two numbers and return the result.
      
      >>> class Calculator:
      ...     def add_two_numbers(self, a, b):
      ...         return a + b
      >>> my_calculator = Calculator()
      >>> add_numbers(my_calculator)
      3
      """
output:     return calculator.add_two_numbers(1, 2)