code: function(model, options) {
        if (!(model instanceof Backbone.Model)) {
          var attrs = model;
          model = new this.model(attrs, {collection: this});
          if (model.validate && !model._performValidation(attrs, options)) model = false;
        } else if (!model.collection) {
          model.collection = this;
        }
        return model;
      }
docs: Prepare a model to be added to this collection