def __init__(self, retriever, observer=None):
        DelegatingRetriever.__init__(self, retriever)
        self.observer = observer
Override this method so that it *updates* the tvtk pipeline
dataset/ETHPy150Open twisted/imaginary/imaginary/idea.py/CanSee.__init__--crossover with--dataset/ETHPy150Open enthought/mayavi/mayavi/modules/glyph.py/Glyph.update_pipeline