Minor mypy related changes and structure refactors

[Raalsky]

Before submitting checklist

• [ ] Did you update the CHANGELOG? (not for test updates, internal changes/refactors or CI/CD setup)
• [ ] Did you ask the docs owner to review all the user-facing changes?

[codecov[bot]]

Codecov Report

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

Project coverage is 81.90%. Comparing base (5942547) to head (8bd84ad).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1820 +/- ## ========================================== + Coverage 77.07% 81.90% +4.82% ========================================== Files 350 212 -138 Lines 19365 9482 -9883 ========================================== - Hits 14926 7766 -7160 + Misses 4439 1716 -2723 ``` | [Flag](https://app.codecov.io/gh/neptune-ai/neptune-client/pull/1820/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=neptune-ai) | Coverage Δ | | |---|---|---| | [macos](https://app.codecov.io/gh/neptune-ai/neptune-client/pull/1820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=neptune-ai) | `80.63% <100.00%> (+4.17%)` | :arrow_up: | | [py3.10](https://app.codecov.io/gh/neptune-ai/neptune-client/pull/1820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=neptune-ai) | `?` | | | [py3.11](https://app.codecov.io/gh/neptune-ai/neptune-client/pull/1820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=neptune-ai) | `?` | | | [py3.12](https://app.codecov.io/gh/neptune-ai/neptune-client/pull/1820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=neptune-ai) | `?` | | | [py3.7](https://app.codecov.io/gh/neptune-ai/neptune-client/pull/1820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=neptune-ai) | `?` | | | [py3.8](https://app.codecov.io/gh/neptune-ai/neptune-client/pull/1820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=neptune-ai) | `77.26% <100.00%> (+0.59%)` | :arrow_up: | | [py3.9](https://app.codecov.io/gh/neptune-ai/neptune-client/pull/1820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=neptune-ai) | `?` | | | [ubuntu](https://app.codecov.io/gh/neptune-ai/neptune-client/pull/1820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=neptune-ai) | `77.14% <100.00%> (+0.56%)` | :arrow_up: | | [unit](https://app.codecov.io/gh/neptune-ai/neptune-client/pull/1820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=neptune-ai) | `77.26% <100.00%> (+0.52%)` | :arrow_up: | | [windows](https://app.codecov.io/gh/neptune-ai/neptune-client/pull/1820/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=neptune-ai) | `80.40% <100.00%> (+4.60%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=neptune-ai#carryforward-flags-in-the-pull-request-comment) to find out more.

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