def _all(self):
        """
        Contains attributes that need to be updated in self.beam_update().
        """
        if self.previous_input is not None and self.previous_layer_inputs is not None:
            return (self.previous_input, self.previous_layer_inputs, self.src)
        else:
            return (self.src,)

        Contains attributes that need to be updated in self.beam_update().
        
utils_nlp/models/transformers/bertsum/decoder.py