code: def _check_if_must_download(request_list, redownload):
      
      for request in request_list:
          request.will_download = (request.save_response or request.return_data) \
                                  and (not request.is_downloaded() or redownload)
docs: Updates request.will_download attribute of each request in request_list.
  
      **Note:** the function mutates the elements of the list!
  
      :param request_list: a list of ``DownloadRequest`` instances
      :type: list[DownloadRequest]
      :param redownload: tells whether to download the data again or not
      :type: bool