docs: public RDFDataset toRDF() throws JsonLdError {
          // TODO: make the default generateNodeMap call (i.e. without a
          // graphName) create and return the nodeMap
          final Map<String, Object> nodeMap = newMap();
          nodeMap.put(JsonLdConsts.DEFAULT, newMap());
          generateNodeMap(this.value, nodeMap);
  
          final RDFDataset dataset = new RDFDataset(this);
  
          for (final String graphName : nodeMap.keySet()) {
              // 4.1)
              if (JsonLdUtils.isRelativeIri(graphName)) {
                  continue;
              }
              final Map<String, Object> graph = (Map<String, Object>) nodeMap.get(graphName);
              dataset.graphToRDF(graphName, graph);
          }
  
          return dataset;
      }