input: Write a python function to calculate the sum of all numbers in a list that are divisible by 3.
  assert divisibleBy3([3, 6, 9, 12]) == 30
  assert divisibleBy3([1, 2, 3, 4, 5, 6]) == 9
  assert divisibleBy3([10, 20, 30, 40, 50]) == 30
output: def divisibleBy3(nums):
      return sum(num for num in nums if num % 3 == 0)