docs: function (contextModel, properties) {
  
                      var ret = [];
  
                      _.each(_.extend({}, properties), function (value, key) {
                          ret.push(key + "=" + value);
                      });
  
                      ret.sort();
  
                      if (contextModel) {
                          ret.unshift(Context.generateCacheIdFromEntity(contextModel));
                      }
  
                      if (ret.length === 0) {
                          return null;
                      }
  
                      return ret.join("&");
                  }