input: Write a function to implement the instruction described in the task. The function should add two numbers and then double the result. Return the final computed value.
  def double_add(num1, num2): 
      return (num1 + num2) * 2
  assert double_add(3, 4)==14
  assert double_add(0, 0)==0
  assert double_add(-1, 1)==0
  assert double_add(5, 5)==20
  assert double_add(-3, -3)==-12
output: def double_add(num1, num2): 
      return (num1 + num2) * 2