code: def _sra_download_worker(*args):
      
      gsm = args[0][0]
      email = args[0][1]
      dirpath = args[0][2]
      kwargs = args[0][3]
      return (gsm.get_accession(), gsm.download_SRA(email, dirpath, **kwargs))
docs: A worker to download SRA files.
  
      To be used with multiprocessing.