nested observables in loops

nested_observables_in_loops.ts

public getKernelAttachments(kernelId: IDBId) {
    this.waitingForFiles = kernelId;
    this.service.getKernelAttachments(kernelId)
      .pipe(
      mergeMap((fileIds: IDBId[]) => {
        const packsArray = fileIds.map((id) => {
          return this.service.getKernelFilePack(id);
        });
        return forkJoin(...packsArray).pipe(
          map((packs) => {
            return packs;
          }),
          catchError((e) => {
            return of(e);
          }),
        );
      }))
      .subscribe((packs) => {
        packs.map((pack) => {
          this.http.get(pack.url, {responseType: 'blob'})
            .subscribe(
              (f) => {
                saveAs(f, pack.name);
                this.notify.create(
                  'The file has saved successfully!',
                  'Your file downloaded successfully and is ready for using!',
                  'success',
                );
                this.waitingForFiles = null;
                },
              (e: HttpErrorResponse) => {
                this.notify.create(
                  'Something went wrong!',
                  `Downloading has failed!<br> Status Code: ${e.status} <br> Message: ${e.statusText}`,
                  'error',
                );
                this.waitingForFiles = null;
              },
            );
        });
      });
  }