Allow mapping over artifact lists

[schustmi]

Describe changes

This PR adds two more items that a step.map(...) call works for:

• A list of output artifacts
• The output of a .map(...) or .product(...) call if the step only returns a single output artifact

Example:

from zenml import pipeline, step

@step
def producer() -> int:
  return 1

@step
def worker(a: int) -> int:
  return a * 2

@pipeline(dynamic=True)
def map_example():
  artifact_list = [producer() for _ in range(3)]
  result = worker.map(artifact_list)  # map over list of outputs
  worker.map(result)  # map over output of previous `map(...)` call

Pre-requisites

Please ensure you have done the following:

• I have read the CONTRIBUTING.md document.
• I have added tests to cover my changes.
• I have based my new branch on develop and the open PR is targeting develop. If your branch wasn't based on develop read Contribution guide on rebasing branch to develop.
• IMPORTANT: I made sure that my changes are reflected properly in the following resources:
  • ZenML Docs
  • Dashboard: Needs to be communicated to the frontend team.
  • Templates: Might need adjustments (that are not reflected in the template tests) in case of non-breaking changes and deprecations.
  • Projects: Depending on the version dependencies, different projects might get affected.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Other (add details above)

[github-actions]

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_{Last checked: 2025-12-05 09:27:25 UTC}