code: def parse_modeString(s):
          
          refresh, width, height = None, None, None
          if '@' in s:
                  s, refresh = s.split('@', 1)
                  refresh = int(refresh)
          if 'x' in s:
                  width, height = [int(x) if x.strip() else None
                                          for x in s.split('x', 1)]
          elif s.strip():
                  width = int(s)
          else:
                  width = None
          return (width, height, refresh)
docs: Parses a modeString like '1024 x 768 @ 60'