input: def divisibleBy3(li: List[int]) -> int:
      """
      Write a simple Python function that takes a list of integers and returns the sum of all elements divisible by 3.
      >>> divisibleBy3([4, 6, 17, 24, 5, 9])
      42
      """
output:     return sum(x for x in li if x % 3 == 0)