[RTR] refactor(maintaining plots)

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Codecov Report

Attention: Patch coverage is 43.24324% with 42 lines in your changes are missing coverage. Please review.

Project coverage is 78.25%. Comparing base (7494252) to head (944c2fe). Report is 48 commits behind head on master.

Files	Patch %	Lines
bioptim/gui/online_callback.py	33.33%	42 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #855 +/- ## ======================================= Coverage 78.25% 78.25% ======================================= Files 139 140 +1 Lines 16228 16230 +2 ======================================= + Hits 12699 12701 +2 Misses 3529 3529 ``` | [Flag](https://app.codecov.io/gh/pyomeca/bioptim/pull/855/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pyomeca) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/pyomeca/bioptim/pull/855/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pyomeca) | `78.25% <43.24%> (+<0.01%)` | :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=pyomeca#carryforward-flags-in-the-pull-request-comment) to find out more.

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pyomeca / bioptim