Make default STEP_METHODS a list that can be modified

[ricardoV94]

Description

Having as a tuple is a bit cumbersome and makes it seem like it should not be modified. However, until we have a more proper system (disptach based probably), this is the API for other packages (including BART, pymc-experimental) to define default samplers.

This PR makes it a list (and over-engineers a fixture for the test :D, happy to remove if you think it's silly)

Related Issue

• [ ] Closes #
• [ ] Related to #

Checklist

• [x] Checked that the pre-commit linting/style checks pass
• [x] Included tests that prove the fix is effective or that the new feature works
• [x] Added necessary documentation (docstrings and/or example notebooks)
• [x] If you are a pro: each commit corresponds to a relevant logical change

Type of change

• [ ] New feature / enhancement
• [ ] Bug fix
• [ ] Documentation
• [x] Maintenance
• [ ] Other (please specify):

[codecov[bot]]

Codecov Report

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

Project coverage is 92.29%. Comparing base (22e8f0b) to head (68457f2).

Additional details and impacted files

[](https://app.codecov.io/gh/pymc-devs/pymc/pull/7231?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pymc-devs) ```diff @@ Coverage Diff @@ ## main #7231 +/- ## ======================================= Coverage 92.29% 92.29% ======================================= Files 101 101 Lines 16892 16892 ======================================= Hits 15590 15590 Misses 1302 1302 ``` | [Files](https://app.codecov.io/gh/pymc-devs/pymc/pull/7231?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pymc-devs) | Coverage Δ | | |---|---|---| | [pymc/step\_methods/\_\_init\_\_.py](https://app.codecov.io/gh/pymc-devs/pymc/pull/7231?src=pr&el=tree&filepath=pymc%2Fstep_methods%2F__init__.py&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pymc-devs#diff-cHltYy9zdGVwX21ldGhvZHMvX19pbml0X18ucHk=) | `100.00% <100.00%> (ø)` | |

[ricardoV94]

The order should not be important, except that for RNG reproducibility it always ends up being important. Repeated entries shouldn't be a problem