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])==42
  assert divisibleBy3([3, 6, 9, 12])==30
  assert divisibleBy3([1, 2, 4, 5])==0
  assert divisibleBy3([15, 9, 21, 3])==48
  assert divisibleBy3([])==0
output: def divisibleBy3(lst):
      return sum(x for x in lst if x % 3 == 0)