centers the editor widget. :qtdoc:`Re-implemented<QStyledItemDelegate.updateEditorGeometry>`

def updateEditorGeometry(self, editor, option, index):
        """centers the editor widget. :qtdoc:`Re-implemented<QStyledItemDelegate.updateEditorGeometry>`"""
        qr = editor.frameGeometry()
        cp = QtGui.QDesktopWidget().availableGeometry().center()
        qr.moveCenter(cp)

        editor.move(qr.topLeft())