assets/js/vendor/backbone-relational.js
function( model, attr, options ) {
			options = options ? _.clone( options ) : {};
			this.setKeyContents( attr );
			this.changed = false;

			var related = this.findRelated( options );
			this.setRelated( related );

			if ( !options.silent ) {
				var dit = this;
				Backbone.Relational.eventQueue.add( function() {
					// The `changed` flag can be set in `handleAddition` or `handleRemoval`
					if ( dit.changed ) {
						dit.instance.trigger( 'change:' + dit.key, dit.instance, dit.related, options, true );
						dit.changed = false;
					}
				});
			}
		}
function( model, attr, options ) {
			options = options ? _.clone( options ) : {};
			this.setKeyContents( attr );
			this.changed = false;

			var related = this.findRelated( options );
			this.setRelated( related );

			if ( !options.silent ) {
				var dit = this;
				Backbone.Relational.eventQueue.add( function() {
					// The `changed` flag can be set in `handleAddition` or `handleRemoval`
					if ( dit.changed ) {
						dit.instance.trigger( 'change:' + dit.key, dit.instance, dit.related, options, true );
						dit.changed = false;
					}
				});
			}
		}
Event handler for `change:<key>`.
If the contents of the key are changed, notify old & new reverse relations and initialize the new relation.