code: def notify_attached(room, event, user):
      
      tpl = get_plugin_template_module('emails/attached.txt', chatroom=room, event=event, user=user)
      _send(event, tpl)
docs: Notifies about an existing chatroom being attached to an event.
  
      :param room: the chatroom
      :param event: the event
      :param user: the user performing the action