Can't redefine method: __filter_banks_getter on class: __torch__.nemo.collections.asr.parts.preprocessing.features.FilterbankFeatures
**Steps/Code to reproduce bug**

I'm trying to repeat the model deployment [instruction ](https://github.com/pytorch/android-demo-app/blob/master/SpeechRecognition/create_wav2vec2.py) on Android.

```python
from torch.utils.mobile_optimizer import optimize_for_mobile

pretrained_model = nemo_asr.models.EncDecCTCModel.load_from_checkpoint(
    "my_model.ckpt",
    map_location="cpu"
)

pretrained_model.eval()
pretrained_model.encoder.freeze()
pretrained_model.decoder.freeze()

quantized_model = torch.quantization.quantize_dynamic(
        pretrained_model, qconfig_spec={torch.nn.Linear}, dtype=torch.qint8, inplace=True
)

scripted_model = torch.jit.script(quantized_model)
# optimized_model = optimize_for_mobile(scripted_model)
```
But torch.jit.script returns an error:
> RuntimeError: Can't redefine method: __filter_banks_getter on class: __torch__.nemo.collections.asr.parts.preprocessing.features.FilterbankFeatures (of Python compilation unit at: ...)

Can you advise how to fix this?
