def arg_list(items, prefix=''):
    """Process a list or string of arguments into a string containing them

    Used so users can pass arguments as a string or list in the configuration file.

    :param items:
    :param prefix:
    :return:
    """
    if not items:
        return ''

    list_of_items = items.split(' ') if isinstance(items, str) else items

    if list_of_items == ['']:
        return ''

    list_of_items = [prefix + i for i in list_of_items]

    return ' '.join(filter(None, list_of_items))