Model reset in QStandardItemModel

When subclassing `QStandardItemModel` a situation arises when the subclass intends to reset the model using `beginResetModel()` and `endResetModel()`. These will emit the `QAbstractItemModel::modelAboutToBeReset()` and `QAbstractItemModel::modelReset()` signals, respectively.

However, between the begin and the end of the model reset the usual model signals will still be emitted as the item model is manipulated.

This does not seem entirely correct, yet I am unaware if this causes trouble for views or proxy models. I'm actually not sure about subclassing `QStandardItemModel` at all, although the doc considers it.