Save figs fix

[A-CGray]

Purpose

In savefigs, we allow the user to pass either a list of formats (e.g ["png", "pdf"]) or a single format string (e.g "png"). In theory, when the user passes in a single string, we convert it to a single entry list so that we always have a list of formats to loop through:

# --- Convert the file format to a list if only one given ---
if not isinstance(formats, Iterable):
   formats = [formats]

However, a string is iterable, so what actually happens when the user passes in a single format string is we don't put it in a list and instead loop over the individual character in the string. So I just changed logic to check if the input is a string.

Expected time until merged

NOW

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

Checklist

• I have run flake8 and black to make sure the Python code adheres to PEP-8 and is consistently formatted
• I have formatted the Fortran code with fprettify or C/C++ code with clang-format as applicable
• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation