code: @SuppressWarnings("unused") // called through reflection by RequestServer
    public ModelIdV3 calcModelId(int version, ModelBuildersV3 m) {
      m.model_builders = new ModelBuilderSchema.IcedHashMapStringModelBuilderSchema();
      String model_id = H2O.calcNextUniqueModelId(m.algo);
      ModelIdV3 mm = new ModelIdV3();
      mm.model_id = model_id;
      return mm;
    }
docs: Calculate next unique model_id.