code: function () {
              if (this._listenerInstalled) {
                  return;
              }
              var self = this,
                  prefix = this.prefix;
  
              var onlyWithPrefix = function (id) {
                  if (_.startsWith(id, prefix)) {
                      return true;
                  }
                  return false;
              };
  
              var withoutPrefix = function (id) {
                  return id.substr(prefix.length);
              };
  
              this.base.on(PREFERENCE_CHANGE, function (e, data) {
                  var prefixedIds = data.ids.filter(onlyWithPrefix);
  
                  if (prefixedIds.length > 0) {
                      self.trigger(PREFERENCE_CHANGE, {
                          ids: prefixedIds.map(withoutPrefix)
                      });
                  }
              });
  
              this._listenerInstalled = true;
          }
docs: @private
  
  Listens for events on the base PreferencesSystem to filter down to the
  events that consumers of this PreferencesSystem would be interested in.