Update modeling_chexagent.py

modeling_chexagent.py

@@ -23,6 +23,7 @@ import torch.nn.functional as F
 import torch.utils.checkpoint
 from torch import nn
 from torch.nn import CrossEntropyLoss
+import transformers
 from transformers.activations import ACT2FN
 from transformers.cache_utils import Cache, DynamicCache
 from transformers.modeling_attn_mask_utils import _prepare_4d_causal_attention_mask