src/transformers/models/sew_d/modeling_sew_d.py/XDropout/backward
class XDropout:    def backward(ctx, grad_output):
        if ctx.scale > 1:
            (mask,) = ctx.saved_tensors
            return grad_output.masked_fill(mask, 0) * ctx.scale, None
        else:
            return grad_output, None