def keep(self, diff):
        """ Mark this diff (or volume) to be kept in path. """
        self._keepVol(diff.toVol)
        self._keepVol(diff.fromVol)
def keep ( self , diff ) : self . _keepVol ( diff . toVol ) self . _keepVol ( diff . fromVol )
Mark this diff (or volume) to be kept in path.