[CORD-2826] Adding support for get_model_class in mock_classes.xproto

Change-Id: I0724b2e5c8baad201f38681f556c4e07fdf77912
diff --git a/lib/xos-genx/xosgenx/targets/mock_classes.xtarget b/lib/xos-genx/xosgenx/targets/mock_classes.xtarget
index 00db7e5..b59a7e5 100644
--- a/lib/xos-genx/xosgenx/targets/mock_classes.xtarget
+++ b/lib/xos-genx/xosgenx/targets/mock_classes.xtarget
@@ -138,6 +138,9 @@
         for store in AllMockObjectStores:
             store.items = []
 
+    def get_model_class(self, classname):
+        return globals()[classname]
+
 model_accessor = ModelAccessor()
 
 class ObjectSet(object):