public function identify(array $credentials)
    {
        /** @var \Authentication\Identifier\IdentifierInterface $identifier */
        foreach ($this->_loaded as $name => $identifier) {
            $result = $identifier->identify($credentials);
            if ($result) {
                return $result;
            }
            $this->_errors[$name] = $identifier->getErrors();
        }

        return null;
    }