How to use the @scion/workbench-application-platform.api.ManifestCommands.FindManifests function in @scion/workbench-application-platform

public onIntent(envelope: MessageEnvelope): void {
    // provide fallback for the former 'query' property of manifest commands
    const command = envelope.message.payload.command || envelope.message.payload.query;
    switch (command) {
      case ManifestCommands.FindManifests: {
        this.queryManifests(envelope as MessageEnvelope);
        break;
      }
      case ManifestCommands.FindManifest: {
        this.queryManifest(envelope as MessageEnvelope);
        break;
      }
      case ManifestCommands.FindCapabilityProviders: {
        this.queryCapabilityProviders(envelope as MessageEnvelope);
        break;
      }
      case ManifestCommands.FindCapabilityConsumers: {
        this.queryCapabilityConsumers(envelope as MessageEnvelope);
        break;
      }
      case ManifestCommands.FindCapability: {

public get manifests$(): Observable {
    const intentMessage: ManifestRegistryIntentMessages.FindManifests = {
      type: PlatformCapabilityTypes.ManifestRegistry,
      qualifier: NilQualifier,
      payload: {
        command: ManifestCommands.FindManifests,
      },
    };

    return Platform.getService(MessageBus).requestReceive$({channel: 'intent', message: intentMessage}, {once: true})
      .pipe(extractMessage([]));
  }