src/transformers/models/big_bird/modeling_big_bird.py/BigBirdForPreTraining/__init__
class BigBirdForPreTraining:    def __init__(self, config):
        super().__init__(config)

        self.bert = BigBirdModel(config, add_pooling_layer=True)
        self.cls = BigBirdPreTrainingHeads(config)

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