code: @SuppressWarnings("unused") // called through reflection by RequestServer
    public ModelBuildersV3 list(int version, ModelBuildersV3 m) {
      m.model_builders = new ModelBuilderSchema.IcedHashMapStringModelBuilderSchema();
      for( String algo : ModelBuilder.algos() ) {
        ModelBuilder builder = ModelBuilder.make(algo, null, null);
        m.model_builders.put(algo.toLowerCase(), (ModelBuilderSchema)SchemaServer.schema(version, builder).fillFromImpl(builder));
      }
      return m;
    }
docs: Return all the modelbuilders.