fix: remove default `bounds` being `None` for #356

[codecov[bot]]

Codecov Report

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

Project coverage is 70.89%. Comparing base (d97482b) to head (c0b3dc8). Report is 7 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #357 +/- ## ========================================== - Coverage 71.59% 70.89% -0.70% ========================================== Files 39 41 +2 Lines 10495 10387 -108 Branches 1407 1130 -277 ========================================== - Hits 7514 7364 -150 - Misses 2517 2562 +45 + Partials 464 461 -3 ``` | [Flag](https://app.codecov.io/gh/tsutterley/pyTMD/pull/357/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tyler+Sutterley) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/tsutterley/pyTMD/pull/357/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tyler+Sutterley) | `70.89% <100.00%> (-0.70%)` | :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=Tyler+Sutterley#carryforward-flags-in-the-pull-request-comment) to find out more.

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