def parse_userinfo(userinfo):
    """Validates the format of user information in a MongoDB URI.
    Reserved characters like ':', '/', '+' and '@' must be escaped
    following RFC 2396.

    Returns a 2-tuple containing the unescaped username followed
    by the unescaped password.

    :Paramaters:
        - `userinfo`: A string of the form <username>:<password>

    .. versionchanged:: 2.2
       Now uses `urllib.unquote_plus` so `+` characters must be escaped.
    """
    if userinfo in '@' or userinfo.count(':') > 1:
        raise InvalidURI("':' or '@' characters in a username or password "
                         "must be escaped according to RFC 2396.")
    user, _, passwd = _partition(userinfo, ":")
    # No password is expected with GSSAPI authentication.
    if not user:
        raise InvalidURI("The empty string is not valid username.")
    user = unquote_plus(user)
    passwd = unquote_plus(passwd)

    return user, passwd
dataset/ETHPy150Open blynch/CloudMemeBackend/pymongo/uri_parser.py/parse_userinfo/swapped operands of `in`