input: Write a python function to multiply each element in a list by a given integer.
  assert multiply_list([1, 2, 3, 4, 5], 2) == [2, 4, 6, 8, 10]
  assert multiply_list([10, 20, 30], 3) == [30, 60, 90]
  assert multiply_list([7, 14, 21], 0) == [0, 0, 0]
output: def multiply_list(lst, n):
      return [x * n for x in lst]