def add_mention(user_mention: str, response: str) -> str:
    """Return response mentioning the person who mentioned you.

    Args:
        user_mention (str): Slack mention.
        response (str): response message.

    Returns:
        str: response message with added mention.
    """
    response_template = "{mention} " + response
    return response_template.format(mention=user_mention)