code: function(attrs, options) {
        if (attrs instanceof Model) {
          if (!attrs.collection) attrs.collection = this;
          return attrs;
        }
        options || (options = {});
        options.collection = this;
        var model = new this.model(attrs, options);
        if (!model._validate(attrs, options)) {
          this.trigger('invalid', this, attrs, options);
          return false;
        }
        return model;
      }
docs: Prepare a hash of attributes (or other model) to be added to this collection.