assets/js/vendor/backbone-relational.js
function( keyContents ) {
			this.keyContents = keyContents;
			this.keyId = Backbone.Relational.store.resolveIdForItem( this.relatedModel, this.keyContents );
		}
function( keyContents ) {
			this.keyContents = keyContents;
			this.keyId = Backbone.Relational.store.resolveIdForItem( this.relatedModel, this.keyContents );
		}
Normalize and reduce `keyContents` to an `id`, for easier comparison
@param {String|Number|Backbone.Model} keyContents