Generate filenames.

    :param tuple sources: Sequence of strings representing path to file(s).
    :return: Path to file(s).
    :rtype: :py:class:`str`

def _generate_filenames(sources):
    """Generate filenames.

    :param tuple sources: Sequence of strings representing path to file(s).
    :return: Path to file(s).
    :rtype: :py:class:`str`
    """
    for source in sources:
        if os.path.isdir(source):
            for path, dirlist, filelist in os.walk(source):
                for fname in filelist:
                    if GenericFilePath.is_compressed(fname):
                        if VERBOSE:
                            print("Skipping compressed file: {}".format(os.path.abspath(fname)))
                        continue
                    else:
                        yield os.path.join(path, fname)

        elif os.path.isfile(source):
            yield source

        elif source.isdigit():
            analysis_id = "AN{}".format(source.zfill(6))
            url = MWREST.format(analysis_id)
            yield url

        elif GenericFilePath.is_url(source):
            yield source

        else:
            raise TypeError("Unknown file source.")