error in tutorial

[styleNie]

Hi, I have install the deepy in windows7, and can run the tutorial1.py in experiments\tutorials, but when I run tutorial2.py, I have got an error like this
C:\Users\Administrator\Desktop\deepy-master\experiments\tutorials>python tutoria
l2.py
Using gpu device 0: GeForce GT 630 (CNMeM is enabled with initial size: 75.0% of
memory, CuDNN not available)
D:\soft\python\lib\site-packages\theano\tensor\signal\downsample.py:6: UserWarni
ng: downsample module has been moved to the theano.tensor.signal.pool module.
"downsample module has been moved to the theano.tensor.signal.pool module.")
INFO:deepy.networks.network:deepy version = 0.2.0
INFO:deepy.dataset.mnist:loading minst data
INFO:deepy.dataset.mnist:[mnist] training data size: 50000
INFO:deepy.dataset.mnist:[mnist] valid data size: 10000
INFO:deepy.dataset.mnist:[mnist] test data size: 10000
INFO:deepy.trainers.trainers:changing optimization method to 'MOMENTUM'
INFO:deepy.networks.network:network inputs: x
INFO:deepy.networks.network:network targets:
INFO:deepy.networks.network:network parameters:
INFO:deepy.networks.network:parameter count: 0
INFO:deepy.trainers.trainers:monitor list: J
INFO:deepy.trainers.trainers:compile evaluation function
INFO:deepy.trainers.trainers:compiling MomentumTrainer learning function
Traceback (most recent call last):
File "tutorial2.py", line 73, in
trainer = MomentumTrainer(model, {'weight_l2': 0.0001})
File "D:\soft\python\lib\site-packages\deepy\trainers\trainers.py", line 436,
in init
super(MomentumTrainer, self).init(network, config, "MOMENTUM")
File "D:\soft\python\lib\site-packages\deepy\trainers\trainers.py", line 354,
in init
learning_updates = list(self.learning_updates())
File "D:\soft\python\lib\site-packages\deepy\trainers\trainers.py", line 381,
in learning_updates
gradients = T.grad(self.cost, params)
File "D:\soft\python\lib\site-packages\theano\gradient.py", line 436, in grad
raise TypeError("cost must be a scalar.")
TypeError: cost must be a scalar.
can you help me?
Thanks!