def METHOD_NAME():
    data = numpy.asarray([[1, 2, 3], [4, 5, 6]], dtype="f")
    model = concatenate(Linear(), Linear())
    model.initialize(data, data)
    Y, backprop = model(data, is_train=True)
    assert Y.shape[1] == sum([layer.predict(data).shape[1] for layer in model.layers])
    dX = backprop(Y)
    assert dX.shape == data.shape