src/transformers/models/ibert/quant_modules.py/SymmetricQuantFunction/backward
class SymmetricQuantFunction:    def backward(ctx, grad_output):
        scale = ctx.scale
        if len(grad_output.shape) == 4:
            scale = scale.view(-1, 1, 1, 1)
        # reshape scale and zeropoint for linear weights
        elif len(grad_output.shape) == 2:
            scale = scale.view(-1, 1)
        else:
            scale = scale.view(-1)

        return grad_output.clone() / scale, None, None, None, None