Method _synchronize

lib/sqlalchemy/orm/dependency.py:612–633

(
        self, state, child, associationrow, clearkeys, uowcommit, pks_changed
    )

                        )

    def _synchronize(
        self, state, child, associationrow, clearkeys, uowcommit, pks_changed
    ):
        source = state
        dest = child
        self._verify_canload(child)
        if dest is None or (
            not self.post_update and uowcommit.is_deleted(dest)
        ):
            return
        if clearkeys:
            sync.clear(dest, self.mapper, self.prop.synchronize_pairs)
        else:
            sync.populate(
                source,
                self.parent,
                dest,
                self.mapper,
                self.prop.synchronize_pairs,
                uowcommit,
                self.passive_updates and pks_changed,
            )

    def _pks_changed(self, uowcommit, state):
        return sync.source_modified(