prepare condition functions

[LilithHafner]

Checklist

• [x] Appropriate tests were added
• [x] Any code changes were done in a way that does not break public API
• [x] All documentation related to code changes were updated
• [x] The new code follows the contributor guidelines, in particular the SciML Style Guide and COLPRAC.
• [x] Any new documentation only uses public API

Additional context

Fixes https://github.com/SciML/diffeqpy/issues/136.

[codecov[bot]]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (0475fc3) 38.81% compared to head (4bfb5bf) 26.38%.

Files	Patch %	Lines
src/callbacks.jl	0.00%	6 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #623 +/- ## =========================================== - Coverage 38.81% 26.38% -12.44% =========================================== Files 55 55 Lines 4261 4249 -12 =========================================== - Hits 1654 1121 -533 - Misses 2607 3128 +521 ```

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