canDropMimeData function not called in treeview

#include <QApplication>

#include <QTreeView>
#include <iostream>
#include <QMimeData>
#include <QHeaderView>

#include <QStandardItemModel>

class SceneTreeModel : public QStandardItemModel
{
    virtual bool canDropMimeData(const QMimeData *data, Qt::DropAction action,
                                 int row, int column, const QModelIndex &parent) const
    {
        std::cout << "canDrop called\n";
        return true;
    }

    virtual QMimeData *mimeData(const QModelIndexList &indexes) const
    {
        QMimeData *mimeData = new QMimeData;
        mimeData->setText("SomeText");
        std::cout << "mimeData provided\n";
        return mimeData;
    }

    /*  as suggested in QTBUG-52044 , does not help
    virtual QStringList mimeTypes() const
    {
        QStringList mts; mts << "x-dragdrop/Item"; return mts;
    }
    */


};

int main( int argc, char **argv )
{
  QApplication app( argc, argv );

  QTreeView *tree = new QTreeView();

  SceneTreeModel model;

  QStandardItem *item1 = new QStandardItem( QString("Item1"));
  model.invisibleRootItem()->appendRow(item1);

  QStandardItem *item2 = new QStandardItem( QString("Item2"));
  item1->appendRow(item2);

  QStandardItem *item3 = new QStandardItem( QString("Item3"));
  model.invisibleRootItem()->appendRow(item3);

  tree->setDragDropMode(QAbstractItemView::InternalMove);

  tree->setModel( &model );
  tree->setRootIsDecorated(false);
  tree->header()->setVisible(false);
  tree->expandAll();


  tree->show();

  return app.exec();
}

import sys

from PyQt5.QtCore import Qt, QMimeData, QLocale
from PyQt5.QtGui import QStandardItemModel, QStandardItem
from PyQt5.QtWidgets import QApplication, QMainWindow, QAbstractItemView, QTreeView


class SceneTreeModel(QStandardItemModel):
    def mimeData(self, indexes):
        print('calling mimeData')

        name = indexes[0].data()

        mimedata = QMimeData()
        mimedata.setText(name)

        return mimedata

    def canDropMimeData(self, data, action, row, column, parent):
        # print(data.text())
        print('can drop called on')
        print(parent.data())
        return True



def give_model():
    model = SceneTreeModel()
    # create a tree item
    item1 = QStandardItem('item1')
    item2 = QStandardItem('item2')
    item3 = QStandardItem('item3')

    model.invisibleRootItem().appendRow(item1)
    item1.appendRow(item2)
    model.invisibleRootItem().appendRow(item3)

    return model


class UI_MainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(UI_MainWindow, self).__init__(parent)
        Left = 250
        Top = 100
        Width = 250
        Height = 300
        self.setGeometry(Left, Top, Width, Height)
        self.setWindowTitle("MainWindow")
        self.setLocale(QLocale(QLocale.English, QLocale.UnitedStates))

        self.treeView = QTreeView(self)
        self.treeView.setRootIsDecorated(False)
        self.treeView.setObjectName("treeView")
        self.treeView.header().setVisible(False)

        self.setCentralWidget(self.treeView)

        self.treeView.setModel(give_model())
        self.treeView.setDragDropMode(QAbstractItemView.InternalMove)
        self.treeView.expandAll()


if __name__ == '__main__':
    MainAppThread = QApplication([])

    MainWindow = UI_MainWindow()
    MainWindow.show()

    sys.exit(MainAppThread.exec_())