Parses `paths` (which may consist of files and/or directories).
    Removes duplicates, sorts, and returns verified srt files.

def prep_files(paths, extensions):
    """Parses `paths` (which may consist of files and/or directories).
    Removes duplicates, sorts, and returns verified srt files."""

    from batchpath import GeneratePaths

    filenames = GeneratePaths().files(paths, os.W_OK, extensions, 0, True)

    if filenames:
        return filenames
    else:
        LOGGER.error('No valid targets were specified')
        sys.exit(1)