src/transformers/models/longformer/modeling_longformer.py/LongformerAttention/__init__
class LongformerAttention:    def __init__(self, config, layer_id=0):
        super().__init__()
        self.self = LongformerSelfAttention(config, layer_id)
        self.output = LongformerSelfOutput(config)
        self.pruned_heads = set()