message: Use class' method to set attribute value
diff: @@ -147,7 +147,7 @@ Finally we check the descriptor size and change it to 128 if it is only 64-dim.
  False
  # So we make it to True to get 128-dim descriptors.
  ->>> surf.extended = True
  +>>> surf.setExtended(True)
  >>> kp, des = surf.detectAndCompute(img,None)
  >>> print( surf.descriptorSize() )
  128
  