class User extends \yii\db\ActiveRecord implements \yii\web\IdentityInterface { public static function findIdentity($id) { return static::findOne(['id' => $id]); } // ... }In this example, the `findIdentity` method is implemented in the `User` model, which extends the `yii\db\ActiveRecord` class and implements the `yii\web\IdentityInterface` interface. The `findIdentity` method takes the `id` of a user as its argument and searches for a record in the database with the specified `id` value. If a record is found, the `findOne` method returns an instance of the `User` model with the values of the record set as its properties. The `findIdentity` function is typically used in conjunction with other authentication and authorization functions, such as `validatePassword` and `login`. The package library that contains the `findIdentity` function is Yii Framework, which is a high-performance PHP framework for web applications.