[bgl-python] write graphviz with position property
From what I can tell it's not possible to correctly wirte a graphviz
file that has a position property (where position is a tuple
of xy) using bgl-python.
The problem, as I see it, is that the wrapper for write_graphviz in
bgl-python writes all the dynamic properties to the graph,
but provides no ability to provide custom writer methods for those
properties. So the resulting graphviz file prints references
to the vertex position *object*, but not its values.
Does anybody have a better suggestion? The only think I can see is to
update the bgl-python wrappers to take function arguments
for custom property writers