How to use the @nebular/theme.NbLayoutDirection.LTR function in @nebular/theme

private updateSidebarIcons(direction: NbLayoutDirection) {
    const [ startSidebar, endSidebar ] = this.sidebars;
    const isLtr = direction === NbLayoutDirection.LTR;
    const startIconClass = isLtr ? 'nb-layout-sidebar-left' : 'nb-layout-sidebar-right';
    const endIconClass = isLtr ? 'nb-layout-sidebar-right' : 'nb-layout-sidebar-left';
    startSidebar.icon = startIconClass;
    endSidebar.icon = endIconClass;
  }

commandProcessor: DemoCommandProcessor
    }),
    NarikUiCoreModule,
    NarikAppCoreModule.forRoot({}),
    NarikJwtAuthenticationModule.forRoot({
      loginEndPoint: "api/account/Authenticate",
      logoutEndPoint: "api/account/Logout",
      refreshEndPoint: "api/account/Authenticate",
      tokenStorage: "localStorage",
      loginPageUrl: "/"
    }),
    NbThemeModule.forRoot(
      { name: "default" },
      undefined,
      undefined,
      NbLayoutDirection.LTR
    ),
    BrowserAnimationsModule,
    NarikClientStorageModule.forRoot(),
    NarikNgxAdmin,
    ShareModule
  ],
  providers: [
    {
      provide: MODULE_DATA_KEY,
      useValue: moduleKey
    },
    {
      provide: MODULE_UI_KEY,
      useValue: moduleKey
    },
    {

commandProcessor: DemoCommandProcessor
    }),
    NarikUiCoreModule,
    NarikAppCoreModule.forRoot({}),
    NarikJwtAuthenticationModule.forRoot({
      loginEndPoint: "api/account/Authenticate",
      logoutEndPoint: "api/account/Logout",
      refreshEndPoint: "api/account/Authenticate",
      tokenStorage: "localStorage",
      loginPageUrl: "/"
    }),
    NbThemeModule.forRoot(
      { name: "default" },
      undefined,
      undefined,
      NbLayoutDirection.LTR
    ),
    BrowserAnimationsModule,
    NarikClientStorageModule.forRoot(),
    NarikNgxAdmin,
    ShareModule
  ],
  providers: [
    {
      provide: MODULE_DATA_KEY,
      useValue: moduleKey
    },
    {
      provide: MODULE_UI_KEY,
      useValue: moduleKey
    },
    {

toggleFlow() {
    const oppositeDirection = this.isRtl
      ? NbLayoutDirection.LTR
      : NbLayoutDirection.RTL;
    this.directionService.setDirection(oppositeDirection);
  }
}