input: 
  def sum_divisible_by_3(numbers: List[int]) -> int:
      """ Given a list of integers, return the sum of all elements divisible by 3.
      >>> sum_divisible_by_3([4, 6, 17, 24, 5, 9])
      45
      >>> sum_divisible_by_3([1, 2, 3, 4, 5])
      3
      """
  
output:     total = 0
      for num in numbers:
          if num % 3 == 0:
              total += num
      return total