getting 'ValueError-TextInputSequence must be str' in 'train_dataset = train_dataset.map(convert_to_features)'
Hello friends,
I want to fine tune longformer QnA for different data. I found this code very relevant to my requirement, so was trying to understand the same thoroughly. but getting an error. 
i am trying to run the same code that Suraj has on github.

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> 'ValueError-TextInputSequence must be str' in 'train_dataset = train_dataset.map(convert_to_features)'.

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`train_dataset  = nlp.load_dataset('squad', split=nlp.Split.TRAIN)
valid_dataset = nlp.load_dataset('squad', split=nlp.Split.VALIDATION)


train_dataset = train_dataset.map(convert_to_features)
valid_dataset = valid_dataset.map(convert_to_features, load_from_cache_file=False)


#patil_suraj
@patil-suraj 
Can you help me with this?