code: def _register_notification_callback(self, connection_handle, attribute_handle, callback, once=False):
          
          notification_id = (connection_handle, attribute_handle)
          with self.notification_callbacks_lock:
              self.notification_callbacks[notification_id] = (callback, once)
docs: Register a callback as a notification callback. It will be called if a notification with the matching
          connection_handle and attribute_handle is received.
  
          Args:
              connection_handle (int): The connection handle to watch
              attribute_handle (int): The attribute handle to watch
              callback (func): The callback function to call once the notification has been received
              once (bool): Should the callback only be called once (and then removed from the notification callbacks)