Flushes data from the SWO buffer.

        After this method is called, the flushed part of the SWO buffer is
        empty.

        If ``num_bytes`` is not present, flushes all data currently in the SWO
        buffer.

        Args:
          self (JLink): the ``JLink`` instance
          num_bytes (int): the number of bytes to flush

        Returns:
          ``None``

        Raises:
          JLinkException: on error

def swo_flush(self, num_bytes=None):
        """Flushes data from the SWO buffer.

        After this method is called, the flushed part of the SWO buffer is
        empty.

        If ``num_bytes`` is not present, flushes all data currently in the SWO
        buffer.

        Args:
          self (JLink): the ``JLink`` instance
          num_bytes (int): the number of bytes to flush

        Returns:
          ``None``

        Raises:
          JLinkException: on error
        """
        if num_bytes is None:
            num_bytes = self.swo_num_bytes()

        buf = ctypes.c_uint32(num_bytes)
        res = self._dll.JLINKARM_SWO_Control(enums.JLinkSWOCommands.FLUSH,
                                             ctypes.byref(buf))
        if res < 0:
            raise errors.JLinkException(res)

        return None