def add_user_to_group(service, group_key, user_email, role):
    """
    Add user to a Google Group.

    :param service: Authenticated directory service object
    :param group_key: Unique identifier of the group (string, email, or id)
    :param user_email: Email of the user
    :param role: Role of the member
    :return: Results of the query
    """
    results = service.members().insert(
        groupKey=group_key,
        body={
            "email": user_email,
            "role": role
        }
    ).execute()

    return results