format output

audio_adjustment.py

@@ -8,7 +8,7 @@ class AudioAdjustmentTool(Tool):
     Inputs are input_path, output_path, level (e.g. 0.5 or -13dB).
     """
     inputs = ["text", "text", "text"]
-    outputs = ["None"]
+    outputs = ["text"]
 
     def __call__(self, input_path: str, output_path: str, level: str):
         (
@@ -16,3 +16,4 @@ class AudioAdjustmentTool(Tool):
             .output(output_path, af="volume={}".format(level))
             .run()
         )
+        return output_path