How to add additional buttons to scriptedsegmenteditoreffect?

I am creating an extension for segment editor using the scriptedsegmenteditoreffect, and I would like to add another button to the widget.
I saw how the on_apply button is added in setupOptionFrame and tried to add another button in a similar fashion

def setupOptionsFrame(self):

    # Object scale slider
    self.objectScaleMmSlider = slicer.qMRMLSliderWidget()
    self.objectScaleMmSlider.quantity = "length"  # get unit, precision, etc. from MRML unit node
    self.objectScaleMmSlider.minimum = 0
    self.objectScaleMmSlider.maximum = 10
    self.objectScaleMmSlider.value = 2.0
    self.objectScaleMmSlider.setToolTip("Increasing this value smooths the segmentation and reduces leaks. This is the sigma used for edge detection.")
    self.scriptedEffect.addLabeledOptionsWidget("Object scale:", self.objectScaleMmSlider)
    self.objectScaleMmSlider.connect("valueChanged(double)", self.updateMRMLFromGUI)

    # Apply button
    self.applyButton = qt.QPushButton("Accept")
    self.applyButton.objectName = self.__class__.__name__ + "Apply"
    self.applyButton.setToolTip("Accept previewed result")
    self.applyButton.connect("clicked()", self.onApply)

    # Do Nothing button
    self.dummyButton = qt.QPushButton("Dummy")
    self.dummyButton.objectName = self.__class__.__name__ + "Dummy"
    self.dummyButton.setToolTip("Dummy things")
    self.dummyButton.connect("clicked()", self.onDummy)

This adds a new button in the widget, but unfortunately I am still missing something since the button does not activate the on_dummy function as hoped. (See the image below)

So how do I get more control over this button that I am adding, or is this not possible when using scriptedsegmenteditoreffect?
If it is possible, then where I can find more information/documentation about this problem?