code: def is_modifier(key):
      
      if _is_str(key):
          return key in all_modifiers
      else:
          if not _modifier_scan_codes:
              scan_codes = (key_to_scan_codes(name, False) for name in all_modifiers) 
              _modifier_scan_codes.update(*scan_codes)
          return key in _modifier_scan_codes
docs: Returns True if `key` is a scan code or name of a modifier key.