code: def _parse_hextet(self, hextet_str):
          
          # Whitelist the characters, since int() allows a lot of bizarre stuff.
          if not self._HEX_DIGITS.issuperset(hextet_str):
              raise ValueError
          if len(hextet_str) > 4:
            raise ValueError
          hextet_int = int(hextet_str, 16)
          if hextet_int > 0xFFFF:
              raise ValueError
          return hextet_int
docs: Convert an IPv6 hextet string into an integer.
  
          Args:
              hextet_str: A string, the number to parse.
  
          Returns:
              The hextet as an integer.
  
          Raises:
              ValueError: if the input isn't strictly a hex number from [0..FFFF].