public function retrieveByCredentials(array $credentials)
{
$user = null;
if (isset($credentials['username'])) {
$user = $this->createModel()->newQuery()->whereUserLogin($credentials['username'])->first();
} elseif (isset($credentials['email'])) {
$user = $this->createModel()->newQuery()->whereUserEmail($credentials['email'])->first();
}
return $user;
}