Hello,
In _collections_abc.py is a private function titled `_check_methods`.
It takes a class and a number of method names (as strings), checks if
the class has all of the methods, and returns NotImplemented if any
are missing. The code is below:
```
def _check_methods(C, *methods):
mro = C._
Dear ChrisA, Steve,
Thank you for your comments.
ChrisA, it was off the main topic, but for me, the issue was just one
of wording in the exception message. It's good to hear changes to
wording can be done without compatibility concerns. I'll find out
about merge request suggested by Stephen J. Tu
