def _user_lookup(key, users):
    """Given a user id and a list of users, search list for user with
       matching id. If found, return user name, else return string 'Not Found'

    Args:
        key (str): User id to match on
        users (list of obj): List of users objects (students)

    Return:
        (str): User name if found, 'Not Found' otherwise
    """
    for user in users:
        if key == user.id:
            return user.name

    return "User Not Found"