Add tests for qtpy sub-module

[K-Meech]

Description

What is this PR

• [ ] Bug fix
• [ ] Addition of a new feature
• [X] Other

Why is this PR needed? The coverage of the qtpy sub-module is currently only 73%

What does this PR do? Increases test coverage on the qtpy sub-module to >90%. Also expands some type hints / docstrings so functions are consistent with each other.

References

Closes https://github.com/brainglobe/brainglobe-utils/issues/63

How has this PR been tested?

All tests pass locally.

Is this a breaking change?

No

Does this PR require an update to the documentation?

No

Checklist:

• [X] The code has been tested locally
• [X] Tests have been added to cover all new functionality (unit & integration)
• [X] The documentation has been updated to reflect any changes
• [X] The code has been formatted with pre-commit

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 89.15%. Comparing base (cacefd6) to head (65df12a). Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #64 +/- ## ========================================== + Coverage 86.49% 89.15% +2.65% ========================================== Files 35 35 Lines 1355 1355 ========================================== + Hits 1172 1208 +36 + Misses 183 147 -36 ```

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