docs: public Vector<Graph<UserStub>> generateAllNodeDataTypeGraphCombinationsOfMaxLength(int length) {
          Vector<Graph<UserStub>> graphs = super.generateAllNodeDataTypeGraphCombinationsOfMaxLength(length);
  
          if (WRITE_STRUCTURES_IN_PARALLEL) {
              // Left as an exercise to the student.
              throw new NotImplementedError();
          } else {
              int i = 0;
              for (Iterator<Graph<UserStub>> iter = graphs.toIterator(); iter.hasNext();) {
                  Graph<UserStub> graph = iter.next();
                  graph.setGraphId("S_" + ++i + "_" + graph.allNodes().size());
                  graph.writeDotFile(outDir + graph.graphId() + ".gv", false, ALSO_WRITE_AS_PNG);
              }
              System.out.println("Wrote " + i + " graph files in DOT format to " + outDir + "");
          }
  
          return graphs;
      }