title: Opencv MOG and GMG subtractor not working
body: <p>i have been going through opencv mog and gmg background subtraction,
  i have installed opencv 3.3.0 from</p>
  
  <p><a href="https://github.com/Itseez/opencv_contrib" rel="nofollow noreferrer">https://github.com/Itseez/opencv_contrib</a></p>
  
  <p>and also opencv from the same version,
  but still i couldn't find MOG not working, where as mog 2 is working,</p>
  
  <pre><code>import numpy as np
  import cv2
  
  cap = cv2.VideoCapture(0)
  
  fgbg = cv2.BackgroundSubtractorMOG()
  
  while(1):
     ret, frame = cap.read()
  
     fgmask = fgbg.apply(frame)
  
     cv2.imshow('frame',fgmask)
     if cv2.waitKey(1) &amp; 0xFF == ord('q'):
          break 
  
  cap.release()
  cv2.destroyAllWindows()
  </code></pre>
  
  <p>i get the following error message</p>
  
  <pre><code>Traceback (most recent call last):
    File "back.py", line 6, in &lt;module&gt;
      fgbg = cv2.BackgroundSubtractorMOG()
  AttributeError: 'module' object has no attribute 'BackgroundSubtractorMOG'
  </code></pre>