langchain/chains/query_constructor/parser.py/QueryTransformer/func_call
class QueryTransformer:    def func_call(self, func_name: Any, *args: Any) -> FilterDirective:
        func = self._match_func_name(str(func_name))
        if isinstance(func, Comparator):
            return Comparison(comparator=func, attribute=args[0][0], value=args[0][1])
        return Operation(operator=func, arguments=args[0])