code: public function init()
      {
          parent::init();
  
          if (!$this->enablePrettyUrl || empty($this->rules)) {
              return;
          }
          if (is_string($this->cache)) {
              $this->cache = Yii::$app->get($this->cache, false);
          }
          if ($this->cache instanceof Cache) {
              $cacheKey = __CLASS__;
              $hash = md5(json_encode($this->rules));
              if (($data = $this->cache->get($cacheKey)) !== false && isset($data[1]) && $data[1] === $hash) {
                  $this->rules = $data[0];
              } else {
                  $this->rules = $this->buildRules($this->rules);
                  $this->cache->set($cacheKey, [$this->rules, $hash]);
              }
          } else {
              $this->rules = $this->buildRules($this->rules);
          }
      }
docs: Initializes UrlManager.