LambdaStep from Sagemaker Workflow requires "WorkflowARN" as an input?

[leitouran]

While trying to create a LambdaStep in a Sagemaker Pipeline using the sagemaker workflow helper, I get the following error:

WorkflowARN key not found in function input! The input received was: {'some" : "stuff", "I need": "on my lambda"'}.

The log for the lambda execution suggests this is a mandatory parameter:

Traceback (most recent call last):
  File "/var/task/schedule_workflow.py", line 25, in lambda_handler
    workflow_arn = get_parameter("WorkflowARN", event)
  File "/var/task/schedule_workflow.py", line 15, in get_parameter
    + " The input received was: 

While it's true I'm not providing such key, there's no clear indication in the Documentation of what this is or how to get it. Plus, no example I've seen of LambdaStep in sagemaker workflows use the WorkflowARN.

It's worth noting that passing the key with a dummy value doesn't fix the issue.

Does anybody know how to fix this?