def paint(self, painter, option, widget=None):
        painter.setBrush(self.brush())
        painter.setPen(self.pen())
        painter.drawEllipse(self.rect())
paint(painter: QPainter, option: QStyleOptionGraphicsItem,
dataset/ETHPy150Open VisTrails/VisTrails/vistrails/packages/vtk/tf_widget.py/TransferFunctionPoint.paint