src/transformers/models/nystromformer/modeling_nystromformer.py/NystromformerAttention/__init__
class NystromformerAttention:    def __init__(self, config, position_embedding_type=None):
        super().__init__()
        self.self = NystromformerSelfAttention(config, position_embedding_type=position_embedding_type)
        self.output = NystromformerSelfOutput(config)
        self.pruned_heads = set()