Return a dictionary of all the messages of this validator, and any subvalidators if present. Keys are message names, values may be a message or list of messages. This is really just intended for documentation purposes, to show someone all the messages that a validator or compound validator (like Schemas) can produce.

@@: Should this produce a more structured set of messages, so that messages could be unpacked into a rendered form to see the placement of all the messages? Well, probably so.

Return any validators that this validator contains. This is not useful for functional, except to inspect what values are available. Specifically the .all_messages() method uses this to accumulate all possible messages.