def _populate_unsaved_relations(self, field_dict):
        for key in self._meta.rel:
            conditions = (
                key is not self._dirty and
                key in field_dict and
                field_dict[key] is None and
                self._obj_cache.get(key) is not None)
            if conditions:
                setattr(self, key, getattr(self, key))
                field_dict[key] = self._data[key]
dataset/ETHPy150Open coleifer/peewee/peewee.py/Model._populate_unsaved_relations/operator `in` -> `is not`