no dmpnn model found

## 🐛 Bug

## To Reproduce

I tried this code:
`
graph_conv_loader = dc.data.CSVLoader(['pKi'], feature_field=smile_field_in_df, featurizer=dc.feat.DMPNNFeaturizer(use_edges=True))
`

found this error:
`AttributeError: module 'deepchem.feat' has no attribute 'DMPNNFeaturizer'`

## Expected behavior

## Environment

* OS:
* Python version:
* DeepChem version:
* RDKit version (optional):
* TensorFlow version (optional):
* PyTorch version (optional):
* Any other relevant information:

## Additional context

installed deepchem in this manner:

pip install --pre deepchem[torch]