Error while running code in CharacterLM.rmd vignettes

[Edmonizel]

I ran into a problem while attempting to follow the code exactly from the provided CharacterLM.rmd in the vignettes folder .

When I run this line of code, it gives the following error:

> train_lm("shakespeare.txt", epochs, max_num_minibatches)

Error in py_call_impl(callable, dots$args, dots$keywords) : 
  AttributeError: 'Variable' object has no attribute 'astype'
Detailed traceback: 
  File "D:\anaconda3\envs\cntk-py36\lib\site-packages\cntk\ops\functions.py", line 393, in __call__
    _, output_map = self.forward(arg_map, outputs)
  File "D:\anaconda3\envs\cntk-py36\lib\site-packages\cntk\internal\swig_helper.py", line 69, in wrapper
    result = f(*args, **kwds)
  File "D:\anaconda3\envs\cntk-py36\lib\site-packages\cntk\ops\functions.py", line 755, in forward
    None, device)
  File "D:\anaconda3\envs\cntk-py36\lib\site-packages\cntk\internal\sanitize.py", line 431, in sanitize_var_map
    batch = sanitize_batch(var, batch, seq_starts, device)
  File "D:\anaconda3\envs\cntk-py36\lib\site-packages\cntk\internal\swig_helper.py", line 69, in wrapper
    result = f(*args, **kwds)
  File "D:\anaconda3\envs\cntk-py36\lib\site-packages\cntk\internal\sanitize.py", line 200, in sanitize_batch
    return Value.create(var, batch, seq_starts, device)
  File "D:\anaconda3\envs\cntk-py
Called from: py_call_impl(callable, dots$args, dots$keywords)

A deeper analysis identified that the problem actually happens at this section of the train_lm() function:

z <- model(input_sequence)

Help on this issue will be greatly appreciated!