Actually, I see that much of my reply isn't really applicable here, since this particular function is only defined for UniformWCS classes anyway.  But I'm using the same design pattern here too.  `inverse()` has the docstring and calls `_inverse`, which is implemented differently for `UniformWCS` and each `LocalWCS` sub-class.  Then each of them don't have to repeat the docstring when they override the implementation from `UniformWCS`.