Get list of sub-folders contained in input folder

    :param folder: input folder to list sub-folders. Default is ``'.'``
    :type folder: str
    :return: list of sub-folders
    :rtype: list(str)

def get_folder_list(folder='.'):
    """ Get list of sub-folders contained in input folder

    :param folder: input folder to list sub-folders. Default is ``'.'``
    :type folder: str
    :return: list of sub-folders
    :rtype: list(str)
    """
    dir_list = get_content_list(folder)
    return [f for f in dir_list if not os.path.isfile(os.path.join(folder, f))]