def respond(challenge, password):
    """
    Respond to a challenge.

    This is useful for challenge/response authentication.

    @param challenge: A challenge.
    @param password: A password.
    @return: The password hashed twice.
    """
    m = md5()
    m.update(password)
    hashedPassword = m.digest()
    m = md5()
    m.update(hashedPassword)
    m.update(challenge)
    doubleHashedPassword = m.digest()
    return doubleHashedPassword

    Respond to a challenge.

    This is useful for challenge/response authentication.

    @param challenge: A challenge.
    @param password: A password.
    @return: The password hashed twice.
    
stackoverflow/venv/lib/python3.6/site-packages/twisted/spread/pb.py