Is there a method that is guaranteed to be executed just before an object 
is garbage collected?
I thought #finalize was it, but looking at senders in the image and 
ObjectMemory code, it appears that this only gets called when something 
that is weakly held gets cleaned up.

The weak apparatus seems to use both finalize and the executor mechanism, 
and I'm not sure what the roles of these two parts are.

I got into this while cleaning up a mess, but I don't really need the 
answers to do so.  I'm just curious.

Happy New Year everyone!