code: def notify(self, subsystem, recipient, subject, body_html, body_text):
          
          if not re.match(self.validation, recipient, re.I):
              raise ValueError('Invalid recipient provided')
  
          if recipient.startswith('#'):
              target_type = 'channel'
  
          elif recipient.find('@') != -1:
              target_type = 'user'
  
          else:
              self.log.error('Unknown contact type for Slack: {}'.format(recipient))
              return
  
          try:
              self._send_message(
                  target_type=target_type,
                  target=recipient,
                  message=body_text,
                  title=subject
              )
          except SlackError as ex:
              self.log.error('Failed sending message to {}: {}'.format(recipient, ex))
docs: You can send messages either to channels and private groups by using the following formats
  
          #channel-name
          @username-direct-message
  
          Args:
              subsystem (`str`): Name of the subsystem originating the notification
              recipient (`str`): Recipient
              subject (`str`): Subject / title of the notification, not used for this notifier
              body_html (`str)`: HTML formatted version of the message, not used for this notifier
              body_text (`str`): Text formatted version of the message
  
          Returns:
              `None`