Use sub_module_dict for completing modules, not its own function

jedi/evaluate/context/namespace.py

@@ -31,7 +31,7 @@ class ImplicitNamespaceContext(Context, SubModuleDictMixin):
         self._paths = paths
 
     def get_filters(self, search_global=False, until_position=None, origin_scope=None):
-        yield DictFilter(self._sub_modules_dict())
+        yield DictFilter(self.sub_modules_dict())
 
     @property
     @evaluator_method_cache()