Opencv python nvidia Optical Flow create with roi

I’m so sorry for asking a basic question.
I want to use nvidia optical flow sdk on opencv python.
I used my code as below and it works well.

                nvof =  cv2.cuda_NvidiaOpticalFlow_2_0.create(half_size, \
                        cv2.cuda.NvidiaOpticalFlow_2_0_NV_OF_PERF_LEVEL_MEDIUM, \
                        cv2.cuda.NvidiaOpticalFlow_2_0_NV_OF_OUTPUT_VECTOR_GRID_SIZE_4, \
                        cv2.cuda.NvidiaOpticalFlow_2_0_NV_OF_HINT_VECTOR_GRID_SIZE_4, \
                        False, False, False, device_id, )

What i want to know is usage of create with roi
cv2.cuda_NvidiaOpticalFlow_2_0.create(size, roidata , …)

In python, what is roidata type and example?