code: function findSuper(methodName, childObject) {
  	var object = childObject;
  	while (object[methodName] === childObject[methodName]) {
  		object = object.constructor.__super__;
  
  		if (!object) {
  			throw new Error('Class has no super method for', methodName, '. Remove the _super call to the non-existent method');
  		}
  	}
  	return object;
  }
docs: Find the next object up the prototype chain that has a different implementation of the method.