Overriding method setModelData
        Editor --> Model

def setModelData(self, editor, model, index):
        """
        Overriding method setModelData
        Editor --> Model
        """
        if not hasattr(model, "set_value"):
            # Read-only mode
            return
        
        if isinstance(editor, QLineEdit):
            value = editor.text()
            try:
                value = display_to_value(to_qvariant(value),
                                         self.get_value(index),
                                         ignore_errors=False)
            except Exception as msg:
                raise
                QMessageBox.critical(editor, _("Edit item"),
                                     _("<b>Unable to assign data to item.</b>"
                                       "<br><br>Error message:<br>%s"
                                       ) % str(msg))
                return
        elif isinstance(editor, QDateEdit):
            qdate = editor.date()
            value = datetime.date( qdate.year(), qdate.month(), qdate.day() )
        elif isinstance(editor, QDateTimeEdit):
            qdatetime = editor.dateTime()
            qdate = qdatetime.date()
            qtime = qdatetime.time()
            value = datetime.datetime( qdate.year(), qdate.month(),
                                       qdate.day(), qtime.hour(),
                                       qtime.minute(), qtime.second() )
        else:
            # Should not happen...
            raise RuntimeError("Unsupported editor widget")
        self.set_value(index, value)