'module' object has no attribute 'BackgroundSubtractorMOG'

bkgnd = cv2.bgsegm.BackgroundSubtractorMOG()

img_sub_gray_image = cv2.cvtColor(img_sub, cv2.COLOR_BGR2GRAY) cv2.error:

bkgnd = cv2.bgsegm.BackgroundSubtractorMOG()
cap = cv2.VideoCapture('video.mp4')

while(True):
    ret, frame = cap.read()

    #background subtraction
    img_sub = bkgnd.apply(frame)

    #convert to grayscale
    img_sub_gray_image = cv2.cvtColor(img_sub, cv2.COLOR_BGR2GRAY)
    #thresholding, forcing to binary image
    ret,threshold1 = cv2.threshold(img_sub_gray_image, LOWER_BOUND, UPPER_BOUND, cv2.THRESH_BINARY)

bkgnd = cv2.bgsegm.BackgroundSubtractorMOG()

cv2.bgsegm.createBackgroundSubtractorMOG()

fgbg = cv2.BackgroundSubtractorMOG2()