Size of image stream in opencv for Python

In Python 3.7 I read an png image with opencv and convert it to an jpg image stream. How can I determine the number of bytes of the stream?

image=cv2.imread('test.png',0)
image_stream = io.BytesIO(cv2.imencode(".jpg",image)[1].tobytes())

>Solution :

(success, data) = cv2.imencode(".jpg", image)
assert success
print(data.nbytes)

This number of bytes is identical to the size of the bytes object returned by the .tobytes() call. Creating a BytesIO() also does not affect this size.