'RobertaTokenizerFast' is not defined

Hey guys! I was using the package to work with chemical reactions using ‘dc.molnet.load_uspto’ as:
tasks, datasets, transformers = dc.molnet.load_uspto(featurizer='RxnFeaturizer', splitter='random')
and since the last update, it doesn’t work anymore, I always get the error msg:

NameError: name 'RobertaTokenizerFast' is not defined

Does anyone know how to resolve this?
Thank you very much!