Raising exceptions instead of using assertions for few models
Author: ghost
Pull request: yes

# What does this PR do?

- The PR addresses issue #12789 in a few transformer scripts.
- Didn't try to tinker a lot of the scripts for the same since it's my 1st PR 

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Fixes # (issue)

## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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      Pull Request section?
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