def __len__(self):
        return len(self._layers)
sets the playback range from a shot node in the scene
dataset/ETHPy150Open lisa-lab/pylearn2/pylearn2/blocks.py/StackedBlocks.__len__--crossover with--dataset/ETHPy150Open eoyilmaz/anima/anima/env/mayaEnv/toolbox.py/Animation.set_range_from_shot