Graphing installed ports

[Ronald F. Guilmette]

Has anyone ever used a graphing tool (such as GraphViz) to create a
graph of all of the installed ports on a given system and their
dependencies?

I think that this would be interesting... and perhaps even useful...
to do, but it seems like such an obvious idea that I have to
guess that somebody else has already coded up a small script to
do this exact thing.  If so, I see no reason why I should re-invent
this wheel.