Wrap directory to pif as a dice extension
    :param files: a list of files, which must be non-empty
    :param kwargs: any additional keyword arguments
    :return: the created pif

def convert(files, **kwargs):
    """
    Wrap directory to pif as a dice extension
    :param files: a list of files, which must be non-empty
    :param kwargs: any additional keyword arguments
    :return: the created pif
    """

    if len(files) < 1:
        raise ValueError("Files needs to be a non-empty list")

    if len(files) == 1:
        if os.path.isfile(files[0]):
            return files_to_pif(files, **kwargs)
        else:
            return directory_to_pif(files[0], **kwargs)
    else:
        return files_to_pif([x for x in files if os.path.isfile(x)], **kwargs)