Sets typing_extensions minimum

[skrawcz]

We are using features that come after 4.0.0 and so we should set the minimum, else users will encounter errors if their version of typing_extensions isn't greater than 4.0.0.

Also fixed places in code where we were not checking appropriately for the right version and importing
from the right place.

Changes

• requirements.txt
• recursive.py

How I tested this

• unit tests

Notes

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.