public function getCredentialsFetcher()
{
$fetcher = null;
if ($this->credentialsFetcher) {
$fetcher = $this->credentialsFetcher;
} elseif ($this->keyFile) {
$fetcher = CredentialsLoader::makeCredentials($this->scopes, $this->keyFile);
} else {
$fetcher = ApplicationDefaultCredentials::getCredentials($this->scopes, $this->authHttpHandler);
}
return new FetchAuthTokenCache($fetcher, $this->authCacheOptions, $this->authCache);
}