[Struct] Refactor split & validate

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.

Project coverage is 99.31%. Comparing base (631da46) to head (e01b458). Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
libreco/utils/validate.py	85.71%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #506 +/- ## ========================================== - Coverage 99.32% 99.31% -0.02% ========================================== Files 129 129 Lines 8447 8448 +1 ========================================== Hits 8390 8390 - Misses 57 58 +1 ``` | [Flag](https://app.codecov.io/gh/massquantity/LibRecommender/pull/506/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=massquantity) | Coverage Δ | | |---|---|---| | [CI](https://app.codecov.io/gh/massquantity/LibRecommender/pull/506/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=massquantity) | `99.31% <92.85%> (-0.02%)` | :arrow_down: | 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=massquantity#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.