Add a filter to the query

        Takes a Filter object, or a filterable DSL object.

def filter(self, f, operator="and"):
        """
        Add a filter to the query

        Takes a Filter object, or a filterable DSL object.
        """
        if self._filtered:
            self._filter_dsl.filter(f)
        else:
            self._build_filtered_query(f, operator)
        return self