Update app.py

app.py

@@ -142,7 +142,7 @@ def parallel(*pairs):
     running_tasks = []
 
     for pair in pairs:
-        f = pair.pop(0)
+        task = pair.pop(0)
         running_tasks.append(Process(target=task, args=(pair,)))
     for running_task in running_tasks:
         running_task.start()