/**
  * Get a session from Redis storage by an associated access token.
  * 
  * @param  \League\OAuth2\Server\Entity\AccessTokenEntity  $accessToken
  * @return \League\OAuth2\Server\Entity\SessionEntity|null
  */
 public function getByAccessToken(AccessTokenEntity $accessToken)
 {
     if (!($token = $this->getValue($accessToken->getToken(), 'oauth_access_tokens'))) {
         return null;
     }
     return $this->get($token['session_id']);
 }