input: Write a function to add two numbers and then double the result. The function should take two parameters, `num1` and `num2`, and return the result of the addition of the two numbers multiplied by 2.
  assert double_add(2, 3)==10
  assert double_add(0, 5)==10
  assert double_add(-1, 1)==0
  assert double_add(-2, -3)==-10
  assert double_add(0, 0)==0
output: def double_add(num1, num2):
      return (num1 + num2) * 2