code: public boolean isVersionedNode(final Graph graph, final Node subject) {
          return listObjects(graph, subject, RDF.type.asNode()).toList().stream().map(Node::getURI)
              .anyMatch((MEMENTO_TYPE)::equals);
      }
docs: Determines whether the subject is of type memento:Memento.
  
  @param graph the graph
  @param subject the subject
  @return whether the subject is a versioned node