From 2e0a6582d541b6146d500c134becd52d393e4070 2014-11-06 19:51:05
From: Min RK <benjaminrk@gmail.com>
Date: 2014-11-06 19:51:05
Subject: [PATCH] don't write orig_nbformat to disk in v3

---

diff --git a/IPython/nbformat/v3/nbjson.py b/IPython/nbformat/v3/nbjson.py
index be9ee28..e074172 100644
--- a/IPython/nbformat/v3/nbjson.py
+++ b/IPython/nbformat/v3/nbjson.py
@@ -56,8 +56,12 @@ class JSONWriter(NotebookWriter):
         kwargs['indent'] = 1
         kwargs['sort_keys'] = True
         kwargs['separators'] = (',',': ')
+        nb = copy.deepcopy(nb)
+        # don't write transient values to disk
+        for key in ('orig_nbformat', 'orig_nbformat_minor'):
+            nb.pop(key, None)
         if kwargs.pop('split_lines', True):
-            nb = split_lines(copy.deepcopy(nb))
+            nb = split_lines(nb)
         return py3compat.str_to_unicode(json.dumps(nb, **kwargs), 'utf-8')