What does the function shuffle (in Train.py line 96) belong to?

[illutheplanet]

When I run Train.py it shows that "NameError: name 'shuffle' is not defined".
Could you tell me what module should I import to avoid that?
There also exists a problem that during feature extraction "Dst tensor is not initialized" always occurs. I reduce the training pair to 28, which is defined in the input1.txt I think? it can be solved. Then problem I mentioned above occurs.
As a new-beginner I just need more information to run your code.