code: public Instant getVersionDate(final Graph graph, final Node subject) {
          final String[] pathParts = subject.getURI().split("/");
          return MEMENTO_LABEL_FORMATTER.parse(pathParts[pathParts.length - 1], Instant::from);
      }
docs: Gets a modification date of a subject from the graph
  
  @param graph the graph
  @param subject the subject
  @return the modification date if it exists