def get_all_layers(self):
        return [self.visible_layer] + self.hidden_layers
data only added once, even after multiple calls to append
dataset/ETHPy150Open lisa-lab/pylearn2/pylearn2/models/dbm/dbm.py/DBM.get_all_layers--crossover with--dataset/ETHPy150Open glue-viz/glue/glue/core/tests/test_data_collection.py/TestDataCollection.test_ignore_multi_add