`usecols` into a compatible format for parsing in `parsers.py`.

    Parameters
    ----------
    usecols : object
        The use-columns object to potentially convert.

    Returns
    -------
    converted : object
        The compatible format of `usecols`.
    Nz}Passing an integer for `usecols` is no longer supported.  Please pass in a list of int from 0 to `usecols` inclusive instead.)