Quick note on pre-commit:

• I think some of the current hadn't been run through pre-commit, so were tweaked a bit by black.
• I set flake8 to allow lines to be 90 characters so it wouldn't error for somethings black won't format (docstrings etc..). We can remove and re-format them by hand if needed!

TODO:

• : If people save metrics as a CSV, then we need to parse their date index as a datetime. (I set everything to use type="arrow" as a placeholder for now, so tests would pass. But we should change before merging).
• : Need to test different overwrite conditions (e.g. when it should error out, check that it works as expected).