Because I can! I just want to ensure that all basic types (for which it makes sense) are correctly and portable pickleable, especially collections and related classes. Note that currently Mapping views are pickleable (as most pure Python classes), but pickle exposes implementation detail (the _mapping attribute). For example pickled keys view of Python implementation of OrderedDict is not fully compatible with C implementation. I want to provide implementation agnostic and more efficient pickling.

>>> keys = collections.abc.KeysView({1: 2, 3: 4})
>>> keys.__reduce_ex__(3)
(<function __newobj__ at 0xb6f64bb4>, (<class 'collections.abc.KeysView'>,), (None, {'_mapping': {1: 2, 3: 4}}), None, None)

There are many ways to do this (msg235477, msg235493). I hesitate with choosing,