code: def save_as_header(self, response, **kwargs):
          
          save_as = kwargs.get('save_as', None)
          if save_as is False:
              return
          file_obj = kwargs.get('file_obj', None)
          if save_as is True or save_as is None:
              filename = os.path.basename(file_obj.path)
          else:
              filename = save_as
          response['Content-Disposition'] = smart_str(
              'attachment; filename=%s' % filename)
docs: * if save_as is False the header will not be added
          * if save_as is a filename, it will be used in the header
          * if save_as is True or None the filename will be determined from the
            file path