Include an example output from _compose_mro()

pep-0443.txt

@@ -190,6 +190,19 @@ argument which includes the relevant ABCs. The algorithm is as follows::
           mro.insert(index, regcls)
       return mro
 
+In its most basic form, it returns the MRO for the given type::
+
+>>> _compose_mro(dict, [])
+[<class 'dict'>, <class 'object'>]
+
+When the haystack consists of ABCs that the specified type is a subclass
+of, they are inserted in a predictable order::
+
+>>> _compose_mro(dict, [Sized, MutableMapping, str, Sequence, Iterable])
+[<class 'dict'>, <class 'collections.abc.MutableMapping'>,
+ <class 'collections.abc.Iterable'>, <class 'collections.abc.Sized'>,
+ <class 'object'>]
+
 While this mode of operation is significantly slower, no caching is
 involved because user code may ``register()`` a new class on an ABC at
 any time. In such case, it is possible to create a situation with