How to use the @ng-bootstrap/ng-bootstrap.NgbDatepickerModule.forRoot function in @ng-bootstrap/ng-bootstrap

SharedRoutingModule,
    // angular
    CommonModule,
    HttpClientModule,
    ReactiveFormsModule,

    // 3rd party UI
    FontAwesomeModule,
    TextMaskModule,

    /**
     * ng-bootstrap modules
     * only those that are used by app
     * should be imported to reduce bundle size
     */
    NgbDatepickerModule.forRoot(),
    NgbCollapseModule.forRoot(),
    NgbModalModule.forRoot(),
    NgbTabsetModule.forRoot(),
    NgbPaginationModule.forRoot(),
    NgbPopoverModule.forRoot(),
    NgbAccordionModule.forRoot(),
    NgbCarouselModule.forRoot(),
    NgbDropdownModule.forRoot(),
  ],
  exports: [
    // angular
    CommonModule,
    HttpClientModule,
    ReactiveFormsModule,

    // 3rd party UI

beforeEach(async(() => {

        TestBed.configureTestingModule({

            imports: [
                BrowserModule,
                DynamicFormsCoreModule,
                DynamicFormsNGBootstrapUIModule,
                FormsModule,
                ReactiveFormsModule,
                NgbButtonsModule,
                NgbModule.forRoot(),
                NgbDatepickerModule.forRoot(),
                NgbTimepickerModule.forRoot(),
                NgbTypeaheadModule.forRoot(),
                TextMaskModule,
                DynamicFormsCoreModule.forRoot(),
                InfiniteScrollModule
            ],
            declarations: [
              DsDynamicScrollableDropdownComponent,
              DsDynamicTypeaheadComponent,
              DsDynamicFormComponent,
              DsDynamicFormControlComponent
            ]

        }).compileComponents().then(() => {

            fixture = TestBed.createComponent(DsDynamicFormControlComponent);

import {
  DsDynamicFormComponent
} from './builder/ds-dynamic-form-ui/ds-dynamic-form.component';
import { DsDynamicTypeaheadComponent } from './builder/model/typeahead/dynamic-typeahead.component';
import { DsDynamicScrollableDropdownComponent } from './builder/model/scrollable-dropdown/dynamic-scrollable-dropdown.component';
import { FormService } from './form.service';
import { FormBuilderService } from './builder/form-builder.service';

@NgModule({
  imports: [
    BrowserModule,
    FormsModule,
    InfiniteScrollModule,
    ReactiveFormsModule,
    NgbModule.forRoot(),
    NgbDatepickerModule.forRoot(),
    NgbTimepickerModule.forRoot(),
    NgbTypeaheadModule.forRoot(),
    DynamicFormsCoreModule.forRoot(),
    DynamicFormsNGBootstrapUIModule,
    TextMaskModule
  ],
  declarations: [
    DsDynamicFormComponent,
    DsDynamicFormControlComponent,
    DsDynamicScrollableDropdownComponent,
    DsDynamicTypeaheadComponent,
    FormComponent,
  ],
  exports: [
    DsDynamicFormComponent,
    DsDynamicFormControlComponent,

import { customValidator, customDateRangeValidator, customAsyncFormGroupValidator } from "./app.validators";

export function mockBackendFactory(mockBackend: MockBackend, baseRequestOptions: BaseRequestOptions) {
    return new Http(mockBackend, baseRequestOptions);
}

@NgModule({

    imports: [
        BrowserModule,
        BrowserAnimationsModule,
        ReactiveFormsModule,
        AppRoutingModule,
        MatNativeDateModule,
        MatCardModule,
        NgbDatepickerModule.forRoot(),
        NgbTimepickerModule.forRoot(),
        //BsDatepickerModule.forRoot(),
        DynamicFormsCoreModule.forRoot(),
        DynamicFormsBasicUIModule,
        DynamicFormsBootstrapUIModule,
        DynamicFormsFoundationUIModule,
        DynamicFormsKendoUIModule,
        DynamicFormsMaterialUIModule,
        DynamicFormsNGBootstrapUIModule,
        DynamicFormsPrimeNGUIModule
    ],
    declarations: [
        BasicSampleFormComponent,
        BootstrapSampleFormComponent,
        FoundationSampleFormComponent,
        KendoSampleFormComponent,