input: Write a function to compute the sum of two numbers and then double the result. The function should accept two parameters representing the numbers to be added and return the doubled sum. If either of the two numbers is negative or the sum exceeds 100, the function should return 0.
  assert double_add(5, 6)==22
  assert double_add(10, 20)==60
  assert double_add(-3, 4)==0
  assert double_add(60, 70)==0
output: def double_add(a, b):
      if a < 0 or b < 0 or a + b > 100:
          return 0
      return (a + b) * 2