From 784692eaeaaf5fd30945749446a48107521e4fd2 Mon Sep 17 00:00:00 2001
From: Ryan Morshead <ryan.morshead@gmail.com>
Date: Sun, 16 Sep 2018 23:14:53 -0700
Subject: [PATCH] preserve class repr after `add_traits`

---
 traitlets/traitlets.py | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/traitlets/traitlets.py b/traitlets/traitlets.py
index be2a8f95..feff34ed 100644
--- a/traitlets/traitlets.py
+++ b/traitlets/traitlets.py
@@ -1399,8 +1399,13 @@ def _register_validator(self, handler, names):
 
     def add_traits(self, **traits):
         """Dynamically add trait attributes to the HasTraits instance."""
-        self.__class__ = type(self.__class__.__name__, (self.__class__,),
-                              traits)
+        cls = self.__class__
+        attrs = {"__module__": cls.__module__}
+        if hasattr(cls, "__qualname__"):
+          # __qualname__ introduced in Python 3.3 (see PEP 3155)
+          attrs["__qualname__"] = cls.__qualname__
+        attrs.update(traits)
+        self.__class__ = type(cls.__name__, (cls,), attrs)
         for trait in traits.values():
             trait.instance_init(self)