code: private static Stream<String> nodeToStringStream(final org.apache.jena.graph.Node object) {
          if (object.isURI()) {
              return of(object.getURI());
          } else if (object.isLiteral()) {
              return of(object.getLiteralValue().toString());
          } else {
              return empty();
          }
      }
docs: Map a Jena Node to a Stream of Strings. Any non-URI, non-Literals map to an empty Stream,
  making this suitable to use with flatMap.