code: protected void checkConstraint(final Optional<Graph> graph, final IRI type, final RDFSyntax syntax) {
          graph.ifPresent(g -> {
              final List<ConstraintViolation> violations = constraintServices.stream().parallel()
                  .flatMap(svc -> svc.constrainedBy(type, g)).collect(toList());
              if (!violations.isEmpty()) {
                  final ResponseBuilder err = status(CONFLICT);
                  violations.forEach(v -> err.link(v.getConstraint().getIRIString(), LDP.constrainedBy.getIRIString()));
                  final StreamingOutput stream = new StreamingOutput() {
                      @Override
                      public void write(final OutputStream out) throws IOException {
                          getServices().getIOService().write(violations.stream().flatMap(v2 -> v2.getTriples().stream()),
                                  out, syntax);
                      }
                  };
                  throw new ClientErrorException(err.entity(stream).build());
              }
          });
      }
docs: Check the constraints of a graph.
  @param graph the graph
  @param type the LDP interaction model
  @param syntax the output syntax