input: Write a python function to find the factors of a given integer from a list.
  assert factors([1, 2, 3, 4, 5, 6], 6) == [1, 2, 3, 6]
  assert factors([2, 4, 6, 8, 10], 20) == [2, 4, 10]
  assert factors([1, 3, 5, 7, 9], 21) == [1, 3, 7]
output: def factors(lst, n):
      return [x for x in lst if n % x == 0]