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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def prompt_for_password(url, user=None, default_user=None):
 """Prompt for username and password. If a user name is passed, only prompt for a password. Args: url (str):
 hostname user (str, optional):
 Pass a valid name to skip prompting for a user name default_user (str, optional):
 Pass a valid name that is used as default when prompting for a user name Raises: KeyboardInterrupt if user hits Ctrl-C Returns: (username, password) or None """

    if user is None:
        default_user = default_user or getpass.getuser()
        while user is None:
            user = compat.console_input(
                "Enter username for {} [{}]: ".format(url, default_user)
            )
            if user.strip() == "" and default_user:
                user = default_user
    if user:
        pw = getpass.getpass(
            "Enter password for {}@{} (Ctrl+C to abort): ".format(user, url)
        )
        if pw or pw == "":
            return (user, pw)
    return None