Week03/sequence_veli_unusdu.py

[veliunusdu]

Removed unused imports and test functions, added utility functions for removing duplicates, counting items, and reversing dictionaries.

Describe your changes

Checklist

• I have read the [CONTRIBUTING]
• I have performed a self-review of my own code
• I have run the code locally and it works as expected
• I have commented my code, particularly in hard-to-understand areas

Screenshots (if appropriate)