@abstractmethod<EOL><INDENT>def get_remembered_encrypted_identity(subject_context):<DEDENT>
pass<EOL>
Based on the given subject context data, retrieves the previously
persisted serialized identity, or None if there is no available data.

:param subject_context: the contextual data, that
                        is being used to construct a Subject instance.

:returns: the previously persisted serialized identity, or None if
          no such data can be acquired for the Subject