thanks @FL33TW00D
stack trace:
ValueErrorTraceback (most recent call last)
 in ()
6     device,
7     scheduler,
----> 8     len(df_train)
9   )
10 print(f’Train loss {train_loss} accuracy {train_acc}’)
2 frames
 in forward(self, input_ids, attention_mask)
9     _, pooled_output = self.xlnet(
10       input_ids=input_ids,
—> 11       attention_mask=attention_mask)
12     output = self.drop(pooled_output)
13     return self.out(output)
ValueError: not enough values to unpack (expected 2, got 1)