unir dos imagenes buscando zonas comunes utilizando opencv2

def unir(imagen1, imagen2):
  img1 = cv2.imread(imagen1,1)
  img2 = cv2.imread(imagen2,1)
  sift = cv2.xfeatures2d.SIFT_create()
  kp1, des1 = sift.detectAndCompute(img1,None)
  kp2, des2 = sift.detectAndCompute(img2,None)
  FLANN_INDEX_KDTREE = 0
  index_params = dict(algorithm = FLANN_INDEX_KDTREE, trees = 5)
  search_params = dict(checks = 50)
  flann = cv2.FlannBasedMatcher(index_params, search_params)
  matches = flann.knnMatch(des1,des2,k=2)
  matchesMask = [[0,0] for i in range(len(matches))]
  for i,(m,n) in enumerate(matches):
      if m