pad_op = dyn_cast_or_null<TF::PadOp>(next_input.getDefiningOp());
    cast_op = dyn_cast_or_null<TF::CastOp>(next_input.getDefiningOp());
  }

  return std::nullopt;
}

// Checks if a convoluton can apply SpaceToDepth transform.
// Only the first convolution in the graph whose batch size smaller than 8
// and its input feature size smaller than 8 can be transformed.
std::optional<BlockArgumentInfo> GetConv2DInputArgNum(TF::Conv2DOp conv2d) {