def set_send_callback(self, callback):
if not hasattr(callback, '<STR_LIT>'):<EOL><INDENT>raise TypeError('<STR_LIT>')<EOL><DEDENT>self.send_callback = callback<EOL>
Sets the send callback function.

If the HDLC controller has already been started, the new
callback function will be taken into account for the next
data frames to be sent.