AttributeError: 'SimBART' object has no attribute 'shared' (End2End Bart)

[En-J-A]

I tried to execute the code with BART using MBartForConditionalGeneration

So
In Bart.py I removed the lines

class MiniBART(MBartModel):
     def __init__(self, config):
         super().__init__(config)
         self.dst_decoder = type(self.decoder)(config, self.shared)
         self.dst_decoder.load_state_dict(self.decoder.state_dict())
   def tie_decoder(self):
         self.shared.padding_idx = self.config.pad_token_id
         self.dst_decoder = type(self.decoder)(self.config, self.shared)
         self.dst_decoder.load_state_dict(self.decoder.state_dict())

and used these lines instead

class SimBART(MBartForConditionalGeneration):
    def __init__(self, config):
        super().__init__(config)
    def tie_decoder(self):
        pass

but I got an error when run with
python train.py --mode train --context_window 2 --pretrained_checkpoint facebook/mbart-large-50 --gradient_accumulation_steps 8 --lr 3e-5 --back_bone bart --cfg seed=557 batch_size=8

the error is

Traceback (most recent call last):
  File "C:\Users\E\train.py", line 363, in <module>
    main()
  File "C:\Users\E\train.py", line 351, in main
    m = Model(args)
  File "C:\Users\train.py", line 35, in __init__
    self.model =  SimBART.from_pretrained(args.model_path if test else 'facebook/mbart-large-50')
  File "C:\Users\E\miniconda3\envs\torch\lib\site-packages\transformers\modeling_utils.py", line 1224, in from_pretrained
    model.tie_weights()
  File "C:\Users\E\miniconda3\envs\torch\lib\site-packages\transformers\modeling_utils.py", line 522, in tie_weights
    output_embeddings = self.get_output_embeddings()
  File "C:\Users\E\BART.py", line 193, in get_output_embeddings
    return _make_linear_from_emb(self.shared)  # make it on the fly
  File "C:\Users\E\miniconda3\envs\torch\lib\site-packages\torch\nn\modules\module.py", line 947, in __getattr__
    raise AttributeError("'{}' object has no attribute '{}'".format(
AttributeError: 'SimBART' object has no attribute 'shared'

what can I do to fix this error?