code: final public P createParametersSchema() {
      // special case, because ModelBuilderSchema is the top of the tree and is parameterized differently
      if (ModelBuilderSchema.class == this.getClass()) {
        return (P)new ModelParametersSchemaV3();
      }
  
      try {
        Class<? extends ModelParametersSchemaV3> parameters_class = ReflectionUtils.findActualClassParameter(this.getClass(), 2);
        return (P)parameters_class.newInstance();
      }
      catch (Exception e) {
        throw H2O.fail("Caught exception trying to instantiate a builder instance for ModelBuilderSchema: " + this + ": " + e, e);
      }
    }
docs: Factory method to create the model-specific parameters schema.