- Added some more type checking

src/Transport/GuzzleClient.php

@@ -12,7 +12,7 @@ class GuzzleClient implements TransportInterface {
     
     public array $headers = [];
     
-    public function push(string $url, array $data) : ? object
+    public function push(string $url, array $data) : object|null|bool
     {
         return ( new Client([
             'timeout'  => $this->timeout,