Adapt multi-period result processing

[SabineHaas]

Description

Please include a summary of the change and which issue is fixed.

Fixes # (issue)

Type of change

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• 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 not work as expected)

Checklist:

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• New and adjusted code is formatted using the pre-commit hooks
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• If new packages are needed, I added them the setup.py
• I have added new features/fixes to the CHANGELOG
• I have added my name to AUTHORS