input: Write a function to create a Python program that adds two numbers and then doubles the result.
  def double_add(num1, num2): 
      return (num1 + num2) * 2
  assert double_add(3, 4)==14
  assert double_add(0, 0)==0
  assert double_add(-2, -1)==-6
  assert double_add(1, -1)==0
  assert double_add(-3, 5)==4
output: def double_add(num1, num2): 
      return (num1 + num2) * 2