I like that you've used a private API as opposed to just poking around in the internal state variables of the Cube. But if we're going to do this it'd be nice if it was via a public API.

That said, a public API providing coords-and-dims would duplicate the functionality already provided by `Cube.coord`/`Cube.coords` and `Cube.coord_dims`.

@esc24 - have you got any thoughts on this?