input: Write a function to print a given string with each character's ASCII code.
  assert print_ascii('A') == 'A : 65'
  assert print_ascii('Hi') == 'H : 72\ni : 105'
  assert print_ascii('abc') == 'a : 97\nb : 98\nc : 99'
output: def print_ascii(s):
      return '\n'.join(f'{char} : {ord(char)}' for char in s)