code: @Deprecated
      public static AsyncSearchQueryResult fromHttp400(String payload) {
          //dummy default values
          SearchStatus status = new DefaultSearchStatus(1L, 1L, 0L);
          SearchMetrics metrics = new DefaultSearchMetrics(0L, 0L, 0d);
  
  
          return new DefaultAsyncSearchQueryResult(
                  status,
                  Observable.<SearchQueryRow>error(new FtsMalformedRequestException(payload)),
                  Observable.<FacetResult>empty(),
                  Observable.just(metrics)
          );
      }
docs: A utility method to convert an HTTP 400 response from the search service into a proper
  {@link AsyncSearchQueryResult}. HTTP 400 indicates the request was malformed and couldn't
  be parsed on the server. As of Couchbase Server 4.5 such a response is a text/plain
  body that describes the parsing error. The whole body is emitted/thrown, wrapped in a
  {@link FtsMalformedRequestException}.
  
  @param payload the HTTP 400 response body describing the parsing failure.
  @return an {@link AsyncSearchQueryResult} that will emit a {@link FtsMalformedRequestException} when calling its
  {@link AsyncSearchQueryResult#hits() hits()} method.
  @deprecated FTS is still in BETA so the response format is likely to change in a future version, and be
  unified with the HTTP 200 response format.