code: public function getToken($tokenId): string
      {
          $this->assertInitialized();
  
          if (empty($this->tokens[$tokenId])) {
              throw new TokenNotFoundException(sprintf('The CSRF token ID "%s" does not exist.', $tokenId));
          }
  
          $this->usedTokens[$tokenId] = true;
  
          return $this->tokens[$tokenId];
      }
docs: {@inheritdoc}