restore single output in chain pipeline stages

api/onnx_web/chain/persist_disk.py

@@ -17,12 +17,12 @@ def persist_disk(
     _params: ImageParams,
     source: Image.Image,
     *,
-    output: List[str],
+    output: str,
     stage_source: Image.Image,
     **kwargs,
 ) -> Image.Image:
     source = stage_source or source
 
-    dest = save_image(server, output[0], source)
+    dest = save_image(server, output, source)
     logger.info("saved image to %s", dest)
     return source

api/onnx_web/output.py

@@ -30,14 +30,14 @@ def hash_value(sha, param: Param):
 
 
 def json_params(
-    output: List[str],
+    outputs: List[str],
     params: ImageParams,
     size: Size,
     upscale: Optional[UpscaleParams] = None,
     border: Optional[Border] = None,
 ) -> Any:
     json = {
-        "output": output,
+        "outputs": outputs,
         "params": params.tojson(),
     }
 

api/onnx_web/serve.py

@@ -760,7 +760,7 @@ def chain():
         context,
         params,
         empty_source,
-        output=output,
+        output=output[0],
         size=size,
         needs_device=device,
     )