code: def close_link(self):
          
          logger.info('Closing link')
          if (self.link is not None):
              self.commander.send_setpoint(0, 0, 0, 0)
          if (self.link is not None):
              self.link.close()
              self.link = None
          self._answer_patterns = {}
          self.disconnected.call(self.link_uri)
docs: Close the communication link.