Crash

`0it [00:00, ?it/s]
0 songs processed
Traceback (most recent call last):
  File "music_generator.py", line 134, in <module>
    x_sample = gibbs_sample(1) 
  File "music_generator.py", line 124, in gibbs_sample
    [_, _, x_sample] = control_flow_ops.While(lambda count, num_iter, *args: count < num_iter,
AttributeError: 'module' object has no attribute 'While'`