[issue31841] Several methods of collections.UserString do not return instances of UserString or its subclasses

[Raymond Hettinger]

Raymond Hettinger <raymond.hettinger at gmail.com> added the comment:

I would support changing format() and format_map().

The join() method has been around for a long time, so changing it might do more harm than good.

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assignee:  -> lisroach
nosy: +lisroach, rhettinger
versions: +Python 3.7

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<https://bugs.python.org/issue31841>
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