def addFiducialObservers(self):
    self.removeFiducialObservers()
    for fiducialList in slicer.util.getNodes('vtkMRMLMarkupsFiducialNode*').values():
      tag = fiducialList.AddObserver(fiducialList.MarkupAddedEvent, self.requestNodeAddedUpdate)
      self.observerTags.append( (fiducialList,tag) )
Add observers to all fiducialLists in scene
dataset/ETHPy150Open acil-bwh/SlicerCIP/Scripted/InteractiveLobeSegmentation/InteractiveLobeSegmentation.py/ILSVisualizationWidget.addFiducialObservers