there is no such thing as cv2.cv2 (probably a typo on your side)
opencv's main repo has :
cv2.createBackgroundSubtractorMOG2()
cv2.createBackgroundSubtractorKNN()
both cv2.createBackgroundSubtractorMOG() and cv2.createBackgroundSubtractorGMG() were moved to the cv2.bgsegm module in opencv_contrib (to use those, you'll have to rebuild cv2 with contrib src)
