docs: def downloadArchiveAction(self, request, queryset):
          '''
          Download selected submissions as archive, for targeted correction.
          '''
          output = io.BytesIO()
          z = zipfile.ZipFile(output, 'w')
  
          for sub in queryset:
              sub.add_to_zipfile(z)
  
          z.close()
          # go back to start in ZIP file so that Django can deliver it
          output.seek(0)
          response = HttpResponse(
              output, content_type="application/x-zip-compressed")
          response['Content-Disposition'] = 'attachment; filename=submissions.zip'
          return response