read_data docstring is erroneous
https://git.gfz-potsdam.de/sec23/korte/paleokalmag/-/blob/master/paleokalmag/data_handling.py#L52 states that it's still possible to provide a DataFrame, which is not the case anymore
https://git.gfz-potsdam.de/sec23/korte/paleokalmag/-/blob/master/paleokalmag/data_handling.py#L52 states that it's still possible to provide a DataFrame, which is not the case anymore