added helpful comments

controller/predicates/has_results_at_layers.js

@@ -2,12 +2,11 @@ const _ = require('lodash');
 const Debug = require('../../helper/debug');
 const debugLog = new Debug('controller:predicates:has_results_at_layers');
 const stackTraceLine = require('../../helper/stackTraceLine');
+
+module.exports = {
   // returns a function that returns true if any result.layer is in any of the
   // supplied layers using array intersection
-
   // example usage: determining if the response contains only admin results
-
-module.exports = {
   any(layers) {
     return (request, response) => {
       const has_results_at_any_layer = !_.isEmpty(
@@ -26,6 +25,9 @@ module.exports = {
 
     };
   },
+  // returns a function that returns true IFF the layers in all the results are
+  // in the supplied layers
+  // example usage: determining if all results are either neighbourhoods or localities
   all(layers) {
     return (request, response) => {
       const has_results_at_all_layers = _.isEmpty(