def query(
        self, search: "SearchBase[_R]", query: Union[str, Query]
    ) -> "SearchBase[_R]":
        """
        Add query part to ``search``.

        Override this if you wish to customize the query used.
        """
        if query:
            if self.fields:
                return search.query("multi_match", fields=self.fields, query=query)
            else:
                return search.query("multi_match", query=query)
        return search

        Add query part to ``search``.

        Override this if you wish to customize the query used.
        
elasticsearch/dsl/faceted_search_base.py