Begin documenting protocol 2.
diff --git a/Lib/pickle.py b/Lib/pickle.py
index d3d1dcf..79ee8af 100644
--- a/Lib/pickle.py
+++ b/Lib/pickle.py
@@ -127,6 +127,22 @@
TRUE = 'I01\n' # not an opcode; see INT docs in pickletools.py
FALSE = 'I00\n' # not an opcode; see INT docs in pickletools.py
+# Protocol 2 (not yet implemented) (XXX comments will be added later)
+
+NEWOBJ = '\x81'
+PROTO = '\x80'
+EXT2 = '\x83'
+EXT1 = '\x82'
+TUPLE1 = '\x85'
+EXT4 = '\x84'
+TUPLE3 = '\x87'
+TUPLE2 = '\x86'
+NEWFALSE = '\x89'
+NEWTRUE = '\x88'
+LONG2 = '\x8b'
+LONG1 = '\x8a'
+LONG4 = '\x8c'
+
__all__.extend([x for x in dir() if re.match("[A-Z][A-Z0-9_]+$",x)])
del x