ASR_with_NeMo Pre-trained Model Inference | Pickling Error 
**Describe the bug**
On attempting inference of a recording, I received the following error:
PicklingError: Can't pickle <class 'nemo.collections.common.parts.preprocessing.collections.AudioTextEntity'>: attribute lookup AudioTextEntity on nemo.collections.common.parts.preprocessing.collections failed

**Steps/Code to reproduce bug**

```
import nemo
import nemo.collections.asr as nemo_asr
asr_model = nemo_asr.models.EncDecCTCModel.from_pretrained(model_name="QuartzNet15x5Base-En", strict=False)

files = ['./soundsample.wav']
for fname, transcription in zip(files, asr_model.transcribe(paths2audio_files=files)):
  print(f"Audio in {fname} was recognized as: {transcription}")
```

**Environment overview**
 - Conda Virtual Environment
 - Method of NeMo install: from source

**Environment details**
- Mac OS Catalina 10.15.7
- PyTorch version: 1.10.1
- Python version: 3.8.5
