How to use the canopen.sdo.client.BlockDownloadStream function in canopen

:returns:
            A file like object.
        """
        buffer_size = buffering if buffering > 1 else io.DEFAULT_BUFFER_SIZE
        if "r" in mode:
            if block_transfer:
                raw_stream = BlockUploadStream(self, index, subindex)
            else:
                raw_stream = ReadableStream(self, index, subindex)
            if buffering:
                buffered_stream = io.BufferedReader(raw_stream, buffer_size=buffer_size)
            else:
                return raw_stream
        if "w" in mode:
            if block_transfer:
                raw_stream = BlockDownloadStream(self, index, subindex, size)
            else:
                raw_stream = WritableStream(self, index, subindex, size, force_segment)
            if buffering:
                buffered_stream = io.BufferedWriter(raw_stream, buffer_size=buffer_size)
            else:
                return raw_stream
        if "b" not in mode:
            # Text mode
            line_buffering = buffering == 1
            return io.TextIOWrapper(buffered_stream, encoding,
                                    line_buffering=line_buffering)
        return buffered_stream

def close(self):
        """Closes the stream."""
        if self.closed:
            return
        super(BlockDownloadStream, self).close()
        if not self._done:
            logger.error("Block transfer was not finished")
        command = REQUEST_BLOCK_DOWNLOAD | END_BLOCK_TRANSFER
        # Specify number of bytes in last message that did not contain data
        command |= (7 - self._last_bytes_sent) << 2
        request = bytearray(8)
        request[0] = command
        if self.crc_supported:
            # Add CRC
            struct.pack_into("