public function modifyPushConfig($subscription, $pushConfig, $optionalArgs = [])
{
$request = new ModifyPushConfigRequest();
$request->setSubscription($subscription);
$request->setPushConfig($pushConfig);
$mergedSettings = $this->defaultCallSettings['modifyPushConfig']->merge(new CallSettings($optionalArgs));
$callable = ApiCallable::createApiCall($this->subscriberStub, 'ModifyPushConfig', $mergedSettings, $this->descriptors['modifyPushConfig']);
return $callable($request, [], ['call_credentials_callback' => $this->createCredentialsCallback()]);
}