--- a/mercurial/templatefilters.py	Sun Apr 23 13:15:30 2017 +0900
+++ b/mercurial/templatefilters.py	Sat Jan 16 19:23:53 2016 +0900
@@ -238,6 +238,7 @@
 
 @templatefilter('json')
 def json(obj, paranoid=True):
+    """Any object. Serializes the object to a JSON formatted text."""
     if obj is None:
         return 'null'
     elif obj is False: