code: function(snap/*, prevChild*/) {
            // check to make sure record does not exist
            var i = this.$indexFor(snap.key);
            if( i === -1 ) {
              // parse data and create record
              var rec = snap.val();
              if( !angular.isObject(rec) ) {
                rec = { $value: rec };
              }
              rec.$id = snap.key;
              rec.$priority = snap.getPriority();
              $firebaseUtils.applyDefaults(rec, this.$$defaults);
  
              return rec;
            }
            return false;
          }
docs: Called to inform the array when a new item has been added at the server.
  This method should return the record (an object) that will be passed into $$process
  along with the add event. Alternately, the record will be skipped if this method returns
  a falsey value.
  
  @param {object} snap a Firebase snapshot
  @param {string} prevChild
  @return {object} the record to be inserted into the array
  @protected