Returns the column instance for this query.
        
        :return     <orb.Column>

def column(self, model=None):
        """
        Returns the column instance for this query.
        
        :return     <orb.Column>
        """
        try:
            schema = (self.__model or model).schema()
        except AttributeError:
            return None
        else:
            return schema.column(self.__column)