code: public function loadUserByUsername($username): User
      {
          $this->framework->initialize();
  
          /** @var User $adapter */
          $adapter = $this->framework->getAdapter($this->userClass);
          $user = $adapter->loadUserByUsername($username);
  
          if (is_a($user, $this->userClass)) {
              return $user;
          }
  
          throw new UsernameNotFoundException(sprintf('Could not find user "%s"', $username));
      }
docs: {@inheritdoc}