input: Write a function that takes a list of integers and returns the sum of all elements 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([3, 6, 9, 12])==30
  assert divisibleBy3([1, 2, 5, 7])==0
  assert divisibleBy3([])==0
  assert divisibleBy3([-3, -6, -9, -12])==-30
output: def divisibleBy3(li):
   total = 0
   for num in li:
    if num % 3 == 0:
     total += num
   return total