input: Write a function to calculate the sum of all elements in a list of integers that are divisible by 3.
  
  def divisibleBy3(li):
   total = 0
   for num in li:
    if num % 3 == 0:
     total += num
   return total
  
  assert divisibleBy3([4, 6, 17, 24, 5, 9])==24
  assert divisibleBy3([1, 2, 3, 4, 5, 6])==9
  assert divisibleBy3([7, 8, 9, 10])==9
  assert divisibleBy3([15, 20, 25, 30])==45
  assert divisibleBy3([])==0
output: def divisibleBy3(li):
   total = 0
   for num in li:
    if num % 3 == 0:
     total += num
   return total