It would be nice if inspect.signature was able to understand bound str.format methods, e.g. `inspect.signature("{a} {b}".format) == inspect.signature(lambda *args, a, b, **kwargs: None)` (`*args, **kwargs` are there because str.format ignores additional arguments).  Right now I believe the only way to parse format strings is string.Formatter, which is slightly less discoverable and harder to use (although it certainly also provides more info, e.g. inspect.signature wouldn't be able to tell about format specifiers, but that's fine).