code: def mimeData(self, indexes):
          
  
          byte_stream = pickle.dumps([self.get_node(index) for index in indexes], pickle.HIGHEST_PROTOCOL)
          mime_data = QMimeData()
          mime_data.setData("application/x-umbragraphmodeldatalist", byte_stream)
          return mime_data
docs: Reimplements the :meth:`QAbstractItemModel.mimeData` method.
  
          :param indexes: Indexes.
          :type indexes: QModelIndexList
          :return: MimeData.
          :rtype: QMimeData