add band checks to knn

[sschmidt23]

Addresses #16 by adding a couple of checks on the bands, ref_band, and mag_limits values. My local pytest is acting up, so I don't know if the tests work or not, I'll create a draft PR to run them here.

Code Quality

• My code follows the code style of this project
• I have written unit tests or justified all instances of #pragma: no cover; in the case of a bugfix, a new test that breaks as a result of the bug has been added
• My code contains relevant comments and necessary documentation for future maintainers; the change is reflected in applicable demos/tutorials (with output cleared!) and added/updated docstrings use the NumPy docstring format
• Any breaking changes, described above, are accompanied by backwards compatibility and deprecation warnings

[sschmidt23]

and, my mouse slipped and I created areal PR, oops.

[sschmidt23]

added some linting changes that make the additions looks more substantial than they really are, tests now run ok and should give more informative error messages. Tagging both @aimalz and @hangqianjun for reviewers.

[hangqianjun]

Sorry for getting back to you for so long!! I somehow skipped this PR. It looks good! Some of these tests may be included in a set of more generic column name tests in tables_io.

[sschmidt23]

@hangqianjun it looks like you are working on essentially the same checks in tables_io, should we maybe just abandon this PR rather than merging it and just let tables_io be responsible for the checks?