def METHOD_NAME(self, client: TembaClient, contact: Contact):
    """
    Add the given contact to the follow-up campaign's group, setting the campaign's
    field key to the current date and time.
    """
    blocked_or_stopped = (
        "blocked" if contact.blocked else "stopped texts from" if contact.stopped else None
    )
    if blocked_or_stopped:
        logger.info(
            "Contact has %s Justfix, so not adding them to group %s",
            self.group_name,
            blocked_or_stopped,
            exc_info=True,
        )
        return
    client.update_contact(
        contact,
        groups=[*contact.groups, get_group(client, self.group_name)],
        fields={**contact.fields, self.field_key: format_iso8601(datetime.datetime.now())},
    )