code: def on_message(self, message):
          
          work_unit = SelenolMessage(message)
          request_id = work_unit.request_id
  
          if message['reason'] == ['selenol', 'request']:
              try:
                  result = self.on_request(work_unit)
                  if result is not None:
                      return {
                          'reason': ['request', 'result'],
                          'request_id': request_id,
                          'content': {
                              'content': result,
                          },
                      }
              except SelenolException as e:
                  logging.exception(e)
                  return {
                      'reason': ['request', 'exception'],
                      'request_id': request_id,
                      'content': {
                          'message': str(e),
                      },
                  }
              except Exception as e:
                  logging.exception(e)
                  return {
                      'reason': ['request', 'exception'],
                      'request_id': request_id,
                      'content': {
                          'message': 'Not a Selenol exception',
                      },
                  }
docs: Message from the backend has been received.
  
          :param message: Message string received.