input: Write a python function to filter numbers that are divisible by 7.
  assert filter_by_seven([14, 21, 28, 35, 42]) == [14, 21, 28, 35, 42]
  assert filter_by_seven([10, 20, 30, 40, 50]) == []
  assert filter_by_seven([7, 14, 21, 22, 23, 24]) == [7, 14, 21]
output: def filter_by_seven(numbers):
      return [num for num in numbers if num % 7 == 0]