code: public static Function<Quad, Quad> skolemizeQuads(final ResourceService svc, final String baseUrl) {
          return quad -> rdf.createQuad(quad.getGraphName().orElse(PreferUserManaged),
                  (BlankNodeOrIRI) svc.toInternal(svc.skolemize(quad.getSubject()), baseUrl), quad.getPredicate(),
                  svc.toInternal(svc.skolemize(quad.getObject()), baseUrl));
      }
docs: Convert quads from an external form to a skolemized form
  @param svc the resource service
  @param baseUrl the base URL
  @return a mapping function