code: def _get_handler(self, node_id):
          
          handler = self._get_attrs(node_id).get(self.HANDLER, self._default_handler)
  
          # Here we make sure the handler is an instance of `BasicNodeHandler` or inherited
          # types. While generally being bad Python practice, we still need it here as an
          # invalid handler can cause IDA to crash.
          if not isinstance(handler, BasicNodeHandler):
              idaapi.msg(("Invalid handler for node {}: {}. All handlers must inherit from"
                          "`BasicNodeHandler`.").format(node_id, handler))
              handler = self._default_handler
          return handler
docs: Get the handler of a given node.