src/transformers/models/big_bird/modeling_big_bird.py/BigBirdLayer/__init__
class BigBirdLayer:    def __init__(self, config, seed=None):
        super().__init__()
        self.config = config
        self.attention_type = config.attention_type
        self.chunk_size_feed_forward = config.chunk_size_feed_forward
        self.seq_len_dim = 1
        self.attention = BigBirdAttention(config, seed=seed)
        self.is_decoder = config.is_decoder
        self.add_cross_attention = config.add_cross_attention
        if self.add_cross_attention:
            if not self.is_decoder:
                raise TypeError(f"{self} should be used as a decoder model if cross attention is added")
            self.crossattention = BigBirdAttention(config)
        self.intermediate = BigBirdIntermediate(config)
        self.output = BigBirdOutput(config)