src/transformers/models/nat/modeling_nat.py/NatDownsampler/__init__
class NatDownsampler:    def __init__(self, dim: int, norm_layer: nn.Module = nn.LayerNorm) -> None:
        super().__init__()
        self.dim = dim
        self.reduction = nn.Conv2d(dim, 2 * dim, kernel_size=(3, 3), stride=(2, 2), padding=(1, 1), bias=False)
        self.norm = norm_layer(2 * dim)