'Create and return the actual Qt widget used for setting this group of
preferences. The widget must implement the
:class:`calibre.gui2.preferences.ConfigWidgetInterface`.
The default implementation uses :attr:`config_widget` to instantiate
the widget.'

def create_widget(self, parent=None):

    (base, _, wc) = self.config_widget.partition(':')
    if (not wc):
        wc = 'ConfigWidget'
    base = importlib.import_module(base)
    widget = getattr(base, wc)
    return widget(parent)
