def commit(transaction):
    """Commit modifications to registered objects.

        Save changes to be made persistent if the transaction commits
        (if `tpc_finish` is called later). If `tpc_abort` is called
        later, changes must not persist.

        This includes conflict detection and handling. If no conflicts
        or errors occur, the data manager should be prepared to make
        the changes persist when `tpc_finish` is called.
        """
