How can I add Groups using Formatting model utils to build a formatting settings model?

try as in the example on the documentation  page ( There are some errors but I'll leave you the correct summarized version below)

import { formattingSettings } from "powerbi-visuals-utils-formattingmodel";
import FormattingSettingsCompositeCard = formattingSettings.CompositeCard;
import FormattingSettingsGroup = formattingSettings.Group;
import FormattingSettingsSlice = formattingSettings.Slice;

// Formatting settings group
class myVisualGroupSettings extends FormattingSettingsGroup {
    // Formatting settings slice
    myAnotherNumericSlice = new formattingSettings.NumUpDown({
        name: "myAnotherNumericSlice",
        displayName: "My Formatting Numeric Slice in group",
        value: 15,
        visible: true,
    });
    slices: Array<FormattingSettingsSlice> = [this.myAnotherNumericSlice];
}

// Formatting settings card
class myVisualCardSettings extends FormattingSettingsCompositeCard {
    name: string = "myVisualCard";
    displayName: string = "My Formatting Card";

    groupSetting = new myVisualGroupSettings(Object())
    groups: Array<FormattingSettingsGroup> = [this.groupSetting]
}

export class VisualFormattingSettingsModel extends FormattingSettingsModel {
    // Create formatting settings model formatting cards
    aCard = new myVisualCardSettings();

    cards = [this.aCard];
}