docs: function(models, at){
          var currentLen = this.length;
  
          models = Array.from(models);
  
          this.act(function(){
              var len = models.length,
                  i = 0;
  
              while(len--){
                  this._add(models[i++], at);
              }
          });
  
          // Signal change when the collection of models change
          if (!this.isActive() && this._changed) {
              this.signalChange();
  
              this.resetChange();
          }
  
          return this;
      }