code: private URI getHasMemberFromResource(final HttpServletRequest request, final FedoraResource resource) {
          return resource.getTriples(translator(request), of(PROPERTIES))
                  .filter(triple -> triple.getPredicate().equals(MEMBERSHIP_RESOURCE.asNode()) && triple.getObject()
                          .isURI())
                  .map(Triple::getObject).map(Node::getURI)
                  .findFirst().map(URI::create).orElse(null);
      }
docs: Get ldp:membershipResource from an existing resource
  
  @param request the request
  @param resource the FedoraResource
  @return URI of the ldp:membershipResource triple or null if not found.