def columns(self, model=None):
        """
        Returns any columns used within this query.

        :return     [<orb.Column>, ..]
        """
        for query in self.__queries:
            for column in query.columns(model=model):
                yield column
def columns ( self , model = None ) : for query in self . __queries : for column in query . columns ( model = model ) : yield column
Returns any columns used within this query.

        :return     [<orb.Column>, ..]