prevent BERT weights from being downloaded twice

examples/summarization/modeling_bertabs.py

@@ -158,7 +158,8 @@ class Bert(nn.Module):
 
     def __init__(self):
         super(Bert, self).__init__()
-        self.model = BertModel.from_pretrained("bert-base-uncased")
+        config = BertConfig.from_pretrained("bert-base-uncased")
+        self.model = BertModel(config)
 
     def forward(self, input_ids, attention_mask=None, token_type_ids=None, **kwargs):
         self.eval()