Fix error loading model with AutoModel

bert_layers.py

@@ -23,6 +23,7 @@ from transformers.models.bert.modeling_bert import BertPreTrainedModel
 from .bert_padding import (index_first_axis,
                                             index_put_first_axis, pad_input,
                                             unpad_input, unpad_input_only)
+from .configuration_bert import BertConfig
 
 try:
     from .flash_attn_triton import flash_attn_qkvpacked_func
@@ -563,6 +564,7 @@ class BertModel(BertPreTrainedModel):
     all_encoder_layers, pooled_output = model(input_ids, token_type_ids, input_mask)
     ```
     """
+    config_class = BertConfig
 
     def __init__(self, config, add_pooling_layer=True):
         super(BertModel, self).__init__(config)