input: Write a python function to convert a string to its corresponding ASCII values.
  assert to_ascii("hello") == [104, 101, 108, 108, 111]
  assert to_ascii("world") == [119, 111, 114, 108, 100]
  assert to_ascii("Python") == [80, 121, 116, 104, 111, 110]
output: def to_ascii(s):
      return [ord(char) for char in s]