code: def stor(ftp=None):
      
      if ftp is None:
          ftp = connect()
          quit = True
      else:
          quit = False
      ftp.voidcmd('TYPE I')
      with contextlib.closing(ftp.transfercmd("STOR " + TESTFN)) as conn:
          chunk = b'x' * BUFFER_LEN
          total_sent = 0
          while True:
              sent = conn.send(chunk)
              total_sent += sent
              if total_sent >= FILE_SIZE:
                  break
      ftp.voidresp()
      if quit:
          ftp.quit()
      return ftp
docs: Same as ftplib's storbinary() but just sends dummy data
      instead of reading it from a real file.