fix #343 by adding step related classes to whitelist

[steven-terrana]

PR Details

fixes #343

Description

adds step related classes to the pipeline whitelist now that library steps are sandboxed when loaded from a folder library source.

How Has This Been Tested

added unit tests that reproduce regression

Types of Changes

• Added Unit Testing
• Docs change / refactoring / dependency upgrade
• 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)

Checklist

• I have added the appropriate label for this PR
• If necessary, I have updated the documentation accordingly.
• All new and existing tests passed.