/**
  * Removes the not assigned tokens.
  *
  * @param Token[] $tokens
  */
 public function cleanUpUnassignedTokens(array $tokens)
 {
     $this->em->clear();
     foreach ($tokens as $token) {
         $token = $this->em->merge($token);
         $this->em->remove($token);
     }
     $this->em->flush();
 }