ExcessHet should perhaps implement ReducibleAnnotation.

[samuelklee]

Seems like there are some commented overrides and method stubs, but there are also some remaining unimplemented methods. See #7394 (comment).

[droazen]

@ldgauthier Thoughts on this?

[samuelklee]

@droazen just for context, I punted on this in the linked PR (I'm not too familiar with the annotation interfaces, and it wasn't immediately obvious to me how to implement the required methods for ExcessHet). So @ldgauthier asked me to file this on the off chance that someone else wants to look at it in the future, but I think it's probably low priority. Seems like someone might have taken a previous unsuccessful stab at it; there were a few vestigial, commented-out //@Override lines.