Clarify that the purpose of computing all the miscellaneous collection types is to register them with the appropriate ABCs.
diff --git a/Lib/collections/abc.py b/Lib/collections/abc.py
index 7fbe84d..37a813a 100644
--- a/Lib/collections/abc.py
+++ b/Lib/collections/abc.py
@@ -18,9 +18,13 @@
"ByteString",
]
-
-### collection related types which are not exposed through builtin ###
-## iterators ##
+# Private list of types that we want to register with the various ABCs
+# so that they will pass tests like:
+# it = iter(somebytearray)
+# assert isinstance(it, Iterable)
+# Note: in other implementations, these types many not be distinct
+# and they make have their own implementation specific types that
+# are not included on this list.
bytes_iterator = type(iter(b''))
bytearray_iterator = type(iter(bytearray()))
#callable_iterator = ???