input: Write a function to calculate the sum of all elements in a given list of integers that are divisible by 3. If the list is empty, return 0.
  assert divisibleBy3([4, 6, 17, 24, 5, 9])==39
  assert divisibleBy3([3, 0, 9, 1, 2])==12
  assert divisibleBy3([7, 11, 13, 17])==0
  assert divisibleBy3([])==0
output: def divisibleBy3(lst):
      return sum(x for x in lst if x % 3 == 0)