src/transformers/models/data2vec/modeling_data2vec_vision.py/Data2VecVisionPooler/__init__
class Data2VecVisionPooler:    def __init__(self, config: Data2VecVisionConfig) -> None:
        super().__init__()
        self.layernorm = (
            nn.LayerNorm(config.hidden_size, eps=config.layer_norm_eps) if config.use_mean_pooling else None
        )