def METHOD_NAME(path):
    """
    Make sure the directory path ends with a slash.
    >>> assert path_prettify('/foo/bar') == '/foo/bar/'
    >>> assert path_prettify('/foo/bar//') == '/foo/bar/'
    :param path: The path to process.
    :type path: str
    :return: Returns the prettified path.
    :rtype: str
    """
    assert isinstance(path, str)
    return '{}/'.format(path.rstrip('/'))