def data(self, index, role):
        if not index.isValid():
            return None
        if role == Qt.DisplayRole or role == Qt.EditRole:
            return self.row_label(index.row())
        if role == Qt.UserRole:
            return self.items[index.row()]
Retrieve data at each index
dataset/ETHPy150Open glue-viz/glue/glue/utils/qt/python_list_model.py/PythonListModel.data