code: def retr(ftp):
      
      ftp.voidcmd('TYPE I')
      with contextlib.closing(ftp.transfercmd("RETR " + TESTFN)) as conn:
          recv_bytes = 0
          while True:
              data = conn.recv(BUFFER_LEN)
              if not data:
                  break
              recv_bytes += len(data)
      ftp.voidresp()
docs: Same as ftplib's retrbinary() but discard the received data.