Add as_dataframe argument to read_csv()

[hagenw]

Relates to #420

This adds the as_dataframe argument to audformat.utils.read_csv(), to have the option to enforce that always a dataframe is returned. The pull request also enhances the documentation of the default behavior, which returns a series if the CSV file holds one column, and an index if the CSV file contains 0 data columns.

[hagenw]

The name always_return_dataframe seems a little bit long to me, do you have some better suggestions we could use instead?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.0%. Comparing base (7b6b683) to head (472bddc).

Additional details and impacted files

Files	Coverage Δ
audformat/core/utils.py	100.0% <100.0%> (ø)

[audeerington]

Cool, seems like a useful option to have!

The name always_return_dataframe seems a little bit long to me, do you have some better suggestions we could use instead?

Maybe return_dataframe or as_dataframe?

[felixbur]

i like "as_dataframe"

[hagenw]

I changed the argument name to as_dataframe and updated the description of the pull request accordingly.