83      * @param callable $httpHandler callback which delivers psr7 request
92         callable $httpHandler = null,  argument
96         $creds = self::getCredentials($scope, $httpHandler, $cacheConfig, $cache);
99         return new AuthTokenSubscriber($creds, $httpHandler);
111      * @param callable $httpHandler callback which delivers psr7 request
122         callable $httpHandler = null,  argument
127         $creds = self::getCredentials($scope, $httpHandler, $cacheConfig, $cache, $quotaProject);
129         return new AuthTokenMiddleware($creds, $httpHandler);
138      * @param callable $httpHandler callback which delivers psr7 request
153         callable $httpHandler = null,  argument
164         if (!$httpHandler) {
170             $httpHandler = HttpHandlerFactory::build($client);
184         } elseif (self::onGce($httpHandler, $cacheConfig, $cache)) {
206      * @param callable $httpHandler callback which delivers psr7 request
215         callable $httpHandler = null,  argument
219         $creds = self::getIdTokenCredentials($targetAudience, $httpHandler, $cacheConfig, $cache);
221         return new AuthTokenMiddleware($creds, $httpHandler);
233      * @param callable $httpHandler callback which delivers psr7 request
242         callable $httpHandler = null,  argument
246         $creds = self::getIdTokenCredentials($targetAudience, $httpHandler, $cacheConfig, $cache);
248         return new ProxyAuthTokenMiddleware($creds, $httpHandler);
257      * @param callable $httpHandler callback which delivers psr7 request
267         callable $httpHandler = null,  argument
275         if (!$httpHandler) {
281             $httpHandler = HttpHandlerFactory::build($client);
298         } elseif (self::onGce($httpHandler, $cacheConfig, $cache)) {