public function addGroup(Communicator $communicator, ProcessedGroup $group): ProcessedMembership
    {
        $response = $communicator->post('api/memberships', new Membership($group->getID(), $this->contactID));
        $returnValue =  RecipientFactory::createProcessedMembershipFromJSON($response);
        if ($this->memberShipsFetched) {
            $this->memberships[] = $returnValue;
        }
        return $returnValue;
    }