code: public function getIsSuperAdmin()
  	{
  		if ($this->_isSuperAdmin !== null) {
  			return $this->_isSuperAdmin;
  		}
  
  		$this->_isSuperAdmin = in_array($this->username, Yii::$app->getModule('auth')->superAdmins);
  		return $this->_isSuperAdmin;
  	}
docs: Returns whether the logged in user is an administrator.
  
  @return boolean the result.