samples: fix python samples compatibility with demo.py

samples/python/gaussian_mix.py

@@ -9,9 +9,10 @@ if PY3:
     xrange = range
 
 import numpy as np
-from numpy import random
 import cv2 as cv
 
+from numpy import random
+
 def make_gaussians(cluster_n, img_size):
     points = []
     ref_distrs = []
@@ -34,7 +35,7 @@ def draw_gaussain(img, mean, cov, color):
     cv.ellipse(img, (x, y), (s1, s2), ang, 0, 360, color, 1, cv.LINE_AA)
 
 
-if __name__ == '__main__':
+def main():
     cluster_n = 5
     img_size = 512
 
@@ -66,4 +67,11 @@ if __name__ == '__main__':
         ch = cv.waitKey(0)
         if ch == 27:
             break
+
+    print('Done')
+
+
+if __name__ == '__main__':
+    print(__doc__)
+    main()
     cv.destroyAllWindows()