How to use the @loopback/core.extensions function in @loopback/core

constructor(
    @inject(CoreBindings.APPLICATION_INSTANCE)
    public app: ApplicationWithRepositories,
    @inject(BootBindings.PROJECT_ROOT) projectRoot: string,
    @extensions()
    public getModelApiBuilders: Getter,
    @config()
    public booterConfig: ArtifactOptions = {},
  ) {
    // TODO assert that `app` has RepositoryMixin members

    super(
      projectRoot,
      // Set booter options if passed in via bootConfig
      Object.assign({}, RestDefaults, booterConfig),
    );
  }

constructor(
    /**
     * Inject a getter function to fetch greeters (bindings tagged with
     * `{[CoreTags.EXTENSION_POINT]: GREETER_EXTENSION_POINT_NAME}`)
     */
    @extensions()
    private getGreeters: Getter,
    /**
     * An extension point should be able to receive its options via dependency
     * injection.
     */
    @config() // Sugar for @inject('services.GreetingService.options', {optional: true})
    public readonly options?: GreetingServiceOptions,
  ) {}

constructor(
    /**
     * Getter for transports
     */
    @extensions(WINSTON_TRANSPORT)
    private transports: Getter,
    /**
     * Getter for formats
     */
    @extensions(WINSTON_FORMAT)
    private formats: Getter,
    /**
     * Configuration for the logger
     */
    @config() private options: LoggerOptions = {},
  ) {}

constructor(
    @extensions()
    protected authenticationStrategies: Getter,
    @inject(AuthenticationBindings.METADATA)
    protected metadata?: AuthenticationMetadata,
  ) {}
  async value(): Promise {

constructor(
    /**
     * Getter for transports
     */
    @extensions(WINSTON_TRANSPORT)
    private transports: Getter,
    /**
     * Getter for formats
     */
    @extensions(WINSTON_FORMAT)
    private formats: Getter,
    /**
     * Configuration for the logger
     */
    @config() private options: LoggerOptions = {},
  ) {}