Document how to use Set and MutableSet as a mixin.
diff --git a/Lib/_abcoll.py b/Lib/_abcoll.py
index 113507a..c241a95 100644
--- a/Lib/_abcoll.py
+++ b/Lib/_abcoll.py
@@ -207,9 +207,9 @@
'''Construct an instance of the class from any iterable input.
Must override this method if the class constructor signature
- will not accept a frozenset for an input.
+ does not accept an iterable for an input.
'''
- return cls(frozenset(it))
+ return cls(it)
def __and__(self, other):
if not isinstance(other, Iterable):