@property<EOL><INDENT>def _related_cache(self):<DEDENT>
try:<EOL><INDENT>return self._related_cache_dict<EOL><DEDENT>except AttributeError:<EOL><INDENT>_related_cache_dict = {}<EOL>self._related_cache_dict = _related_cache_dict<EOL>return _related_cache_dict<EOL><DEDENT>
A cache for storing related objects already retrieved from
        mongo.