code: def cat(src_filename, dst_file):
      
      (dev, dev_filename) = get_dev_and_path(src_filename)
      if dev is None:
          with open(dev_filename, 'rb') as txtfile:
              for line in txtfile:
                  dst_file.write(line)
      else:
          filesize = dev.remote_eval(get_filesize, dev_filename)
          return dev.remote(send_file_to_host, dev_filename, dst_file, filesize,
                            xfer_func=recv_file_from_remote)
docs: Copies the contents of the indicated file to an already opened file.