(self, labels, indexes, cost)
record the query history
record the query history
record the query history
def _update_query_history(self, labels, indexes, cost):
        """record the query history"""
        self._query_history.append(((labels, cost), indexes))
def _update_query_history ( self , labels , indexes , cost ) : self . _query_history . append ( ( ( labels , cost ) , indexes ) )