# ask-the-community

Nandakumar Raghu

06/26/2023, 2:57 PM
Hi, I am seeing this error when trying to register my workflow -
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Failed with Unknown Exception <class 'AssertionError'> Reason: Cannot pass output from task n3 that produces no outputs to a downstream task
How do I find more information about this. Which task is this referring to?

Kevin Su

06/26/2023, 4:05 PM
There is a task supposed to create a output, but it didn’t. would you mind sharing your workflow code? we can improve error message.

Victor Churikov

06/26/2023, 4:46 PM
In my experience this error was caused by not specifying the output type for a task such as:
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def mytask(input1: str):
    return input1
This change made it work:
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def mytask(input1: str) -> str:
    return input1
Look through your tasks for a task that is supposed to return something but doesn’t specify which type it returns. Also make sure that you are not trying to receive as an input the promise from a task that isn’t supposed to return anything

Nandakumar Raghu

06/26/2023, 10:46 PM
Ok, thanks! I will check that.