So this is close to what I had in mind. As written though, you can only pass in one of these things, which is unduly restricting given that there's no reason someone validating dates doesn't necessarily want to also validate internet stuff, so I really had in mind that they all be combined together in ``FormatChecker`` itself, and then in the docs you just make up some new format that was just for example purposes. This way all the default formats can be enabled together.

After thinking about it a little more though, I think we can do even better than that though. I think we should stick with FormatChecker, and give it all those methods, but instead of dispatching by doing a `getattr` on is_whatever, give FormatChecker a decorator that registers a function for a given format (store it on `FormatChecker.checkers`, a `dict`). So

```
@FormatChecker.checks("regex")
def is_regex(stuff):
    whatever
```

Let me know if that's clear enough or if you don't know how to do that or whatever.