code: public static List<Node> nodesFromJSON(Model mo, JSONArray a) throws JSONConverterException {
          String json = a.toJSONString();
          List<Node> s = nodesCache.get(json);
          if (s != null) {
              return s;
          }
          s = new ArrayList<>(a.size());
          for (Object o : a) {
              s.add(getNode(mo, (int) o));
          }
          nodesCache.put(json, s);
          return s;
      }
docs: Convert an array of VM identifiers to a set of VMs.
  This operation uses a cache of previously converted set of nodes.
  @param mo the associated model to browse
  @param a the json array
  @return the set of nodes