Fix mutable defaults in documentation example (pynamodb#507)

MHannila · garrettheel · commit 0f15bb1573e0 · 2018-07-03T08:50:03.000-07:00
diff --git a/docs/updates.rst b/docs/updates.rst
@@ -20,9 +20,9 @@ Suppose that you have defined a `Thread` Model for the examples below.
             table_name = 'Thread'
 
         forum_name = UnicodeAttribute(hash_key=True)
-        subjects = UnicodeSetAttribute(default={})
+        subjects = UnicodeSetAttribute(default=dict)
         views = NumberAttribute(default=0)
-        notes = ListAttribute(default=[])
+        notes = ListAttribute(default=list)
 
 
 .. _updates:
