<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _decode_key(self, key):
 """Decode key using hex_codec to retrieve the original key. Keys are returned as :class:`str` if serialization is enabled. Keys are returned as :class:`bytes` if serialization is disabled. """

        bkey = codecs.decode(key.encode(self._keyencoding), 'hex_codec')
        return bkey.decode(self._keyencoding) if self._serialize else bkey