retval return variable output and format on OpenCV2 python

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I'm having some trouble understanding retval on some function in OpenCV2, some of it will only returning one variable and another returning up to four variable.

I want to understand what type of data it returning, such as BoundingRectwill returning x,y,width, height. and cv2.useOptimized will return 1 or 0 instead. how can i determine type of output (boolean, array, image, etc) from OpenCV manual?

should i determine the output from it's C++ function?