input: Write a function to add two numbers and then double the result.
  
  def double_add(num1, num2): 
      return (num1 + num2) * 2
  
  assert double_add(2, 3) == 10
  assert double_add(-1, 5) == 8
  assert double_add(0, 0) == 0
  assert double_add(-4, -3) == -14
  assert double_add(1, 1) == 4
output: def double_add(num1, num2): 
      return (num1 + num2) * 2