code: String composeMembershipId(Node groupNode, Node refUserNode, Node refTypeNode) throws RepositoryException
     {
        return groupNode.getUUID()
           + ','
           + refUserNode.getName()
           + ','
           + (refTypeNode.getName().equals(JCROrganizationServiceImpl.JOS_MEMBERSHIP_TYPE_ANY)
              ? MembershipTypeHandler.ANY_MEMBERSHIP_TYPE : refTypeNode.getName());
     }
docs: Compose membership identifier. For more information see {@link MembershipImpl}