input: 
  def double_add(num1, num2):
      """
      Generate a Python program that adds two numbers and then doubles the result.
  
      >>> double_add(1, 2)
      6
      >>> double_add(-3, 3)
      0
      """
      return (num1 + num2) * 2
  
output:     return (num1 + num2) * 2