src/transformers/models/bert_generation/modeling_bert_generation.py/BertGenerationDecoder/__init__
class BertGenerationDecoder:    def __init__(self, config):
        super().__init__(config)

        if not config.is_decoder:
            logger.warning("If you want to use `BertGenerationDecoder` as a standalone, add `is_decoder=True.`")

        self.bert = BertGenerationEncoder(config)
        self.lm_head = BertGenerationOnlyLMHead(config)

        # Initialize weights and apply final processing
        self.post_init()