ConnectionError: Couldn't reach 'allenai/c4' on the Hub (ConnectionError)数据集下不下来，怎么回事
### Describe the bug

from datasets import load_dataset
print("11")
traindata = load_dataset('ptb_text_only', 'penn_treebank', split='train')
print("22")
valdata = load_dataset('ptb_text_only',
                           'penn_treebank',
                           split='validation')

### Steps to reproduce the bug

1

### Expected behavior

1

### Environment info

1