input: Write a python function to convert a list of strings to a list of integers.
  assert str_to_int(["1", "2", "3"]) == [1, 2, 3]
  assert str_to_int(["10", "20", "30"]) == [10, 20, 30]
  assert str_to_int(["0", "-1", "5"]) == [0, -1, 5]
output: def str_to_int(lst):
      return [int(x) for x in lst]