Can you show me some code?

I think I understand what is going on. There are a bunch of things that will break here. 1. Parameters can’t be functions. They need to be JSONSerializeable. This might work for

flow.run()

but will break for runs with Prefect Cloud because those are triggered by API requests. Instead, use a string as a default and pass it to an intermediate task to return the function/callable 2. I am unclear at the moment if

get_sequences_attr

is a task. If it is a task, you can’t use

for

loops on task outputs because

for

runs during the Flow

build

time, not during

flow.run()

. So the Flow is built, but the

for

loop doesn’t know how many items there are in the list if it’s a Task. A Task value (including Parameters) are created at runtime. Note the distinction of flow-build and flow-run time. If you need to loop over a task output, you should be looking at mapping. 3. Assuming

sequence_attr

is some task output, you can’t do stuff like

sequence_attr.get_path()

. This is because that is evaluated during build time when it is still type Task. The value doesn’t exist until runtime. Instead, you need this method class to happen inside a task so logic is deferred. This will work though if

sequence_attr

is not a task and already defined during flow-build time.

4. If

get_sequences_attr

is a function, you can’t pass a Parameter to it because Parameters don’t exist during build time. It will not behave as expected and you are passing the Parameter class as opposed to a Parameter value

It might be helpful for you to use Tasks for everything in the Flow block at first, because that is how work gets deferred to

flow.run()

I hope that helps!