Add Ptr KNearest::load and python binding

modules/ml/misc/python/test/test_knearest.py

@@ -0,0 +1,13 @@
+#!/usr/bin/env python
+import cv2 as cv
+
+from tests_common import NewOpenCVTests
+
+class knearest_test(NewOpenCVTests):
+    def test_load(self):
+        k_nearest = cv.ml.KNearest_load(self.find_file("ml/opencv_ml_knn.xml"))
+        self.assertFalse(k_nearest.empty())
+        self.assertTrue(k_nearest.isTrained())
+
+if __name__ == '__main__':
+    NewOpenCVTests.bootstrap()