code: function pointToQuery(url, requestFormatter, responseFormatter) {
  	  return function (inputSource) {
  	    return function outputSource(start, outputSink) {
  	      if (start !== 0) return;
  	      inputSource(0, function (t, d) {
  	        if (t === 1) {
  	          var queryUrl = requestFormatter(url, { x: d.latlng.lng, y: d.latlng.lat });
  	          query(queryUrl).then(function (res) {
  	            var output = {
  	              queryResult: responseFormatter(res),
  	              latlng: d.latlng
  	            };
  	            outputSink(1, output);
  	          });
  	        } else {
  	          outputSink(t, d);
  	        }
  	      });
  	    };
  	  };
  	}
docs: transforming operator returns an object with original latlng and queryResult: { queryResult: {}, latlng: d.latlng } user-supplied responseFormatter is used to create queryResult.