input: Write a function to convert a string to its corresponding unicode values.
  assert string_to_unicode("hello") == [104, 101, 108, 108, 111]
  assert string_to_unicode("world") == [119, 111, 114, 108, 100]
  assert string_to_unicode("python") == [112, 121, 116, 104, 111, 110]
output: def string_to_unicode(s):
      return [ord(char) for char in s]