"ASR_with_NeMo.ipynb" TypeError: TypeError: NeuralTypeComparisonResult.INCOMPATIBLE : Input type expected : axes: (batch, time); elements_type: AudioSignal   input param_0 : freq: 16000 Input type found : axes: (batch, time); elements_type: VoidType
State: closed | Pull request: no
Labels: name: bug

Hi There,

I'm trying to run "ASR_with_NeMo.ipynb" in tutorials directory. In the section `Using an Out-of-the-Box Model`, I can successfully load `QuartzNet15x5Base-En`, but when I run `quartznet.transcribe(paths2audio_files=files)`, I get the following error:


```
TypeError: NeuralTypeComparisonResult.INCOMPATIBLE :
Input type expected : axes: (batch, time); elements_type: AudioSignal
  input param_0 : freq: 16000
Input type found : axes: (batch, time); elements_type: VoidType
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-10-fa3a7fc9cc2a> in <module>
      1 files = ['./an4/wav/an4_clstk/mgah/cen2-mgah-b.wav']
----> 2 for fname, transcription in zip(files, quartznet.transcribe(paths2audio_files=files)):
      3   print(f"Audio in {fname} was recognized as: {transcription}")

~/anaconda3/envs/nemo/lib/python3.8/site-packages/torch/autograd/grad_mode.py in decorate_context(*args, **kwargs)
     26         def decorate_context(*args, **kwargs):
     27             with self.__class__():
---> 28                 return func(*args, **kwargs)
     29         return cast(F, decorate_context)
     30 

NeMo/nemo/collections/asr/models/ctc_models.py in transcribe(self, paths2audio_files, batch_size, logprobs, return_hypotheses)
    236                 temporary_datalayer = self._setup_transcribe_dataloader(config)
    237                 for test_batch in tqdm(temporary_datalayer, desc="Transcribing"):
--> 238                     logits, logits_len, greedy_predictions = self.forward(
    239                         input_signal=test_batch[0].to(device), input_signal_length=test_batch[1].to(device)
    240                     )

NeMo/nemo/core/classes/common.py in __call__(self, wrapped, instance, args, kwargs)
    770 
    771         # Perform rudimentary input checks here
--> 772         instance._validate_input_types(input_types=input_types, ignore_collections=self.ignore_collections, **kwargs)
    773 
    774         # Call the method - this can be forward, or any other callable method

NeMo/nemo/core/classes/common.py in _validate_input_types(self, input_types, ignore_collections, **kwargs)
    208                     for i, dict_tuple in enumerate(value.neural_type.elements_type.type_parameters.items()):
    209                         error_msg.append(f'  input param_{i} : {dict_tuple[0]}: {dict_tuple[1]}')
--> 210                     raise TypeError("\n".join(error_msg))
    211 
    212                 # Perform input ndim check

TypeError: NeuralTypeComparisonResult.INCOMPATIBLE :
Input type expected : axes: (batch, time); elements_type: AudioSignal
  input param_0 : freq: 16000
Input type found : axes: (batch, time); elements_type: VoidType

```

Thanks in advance for your help.