def find_by_user_name(cls,user_name):
    """
    Method that takes in a user_name and returns a user that matches that number.

    Args:
    user_name: User_name to search for 
    Returns: 
    User of person that matches the user_name.
    """
    for user in cls.user_list:
        if user.user_name == user_name:
            return user