Tools such as ruff can ignore "imported but unused" warnings if a
line ends with "# noqa: F401". It avoids the temptation to remove
an import which is used effectively.
* Allow to specify the signature of custom callable instances of extension
type by the __text_signature__ attribute.
* Specify signatures of operator.attrgetter, operator.itemgetter, and
operator.methodcaller instances.
Having `operator.call(obj, arg)` mean `type(obj).__call__(obj, arg)` is
consistent with the other dunder operators. The semantics with `*args,
**kwargs` then follow naturally from the single-arg semantics.
requires them. Disable executable bits and shebang lines in test and
benchmark files in order to prevent using a random system python, and in
source files of modules which don't provide command line interface. Fixed
shebang lines in the unittestgui and checkpip scripts.
