Add Ptr KNearest::load and python binding

modules/ml/src/knearest.cpp

@@ -515,6 +515,17 @@ Ptr<KNearest> KNearest::create()
     return makePtr<KNearestImpl>();
 }
 
+Ptr<KNearest> KNearest::load(const String& filepath)
+{
+    FileStorage fs;
+    fs.open(filepath, FileStorage::READ);
+
+    Ptr<KNearest> knearest = makePtr<KNearestImpl>();
+
+    ((KNearestImpl*)knearest.get())->read(fs.getFirstTopLevelNode());
+    return knearest;
+}
+
 }
 }