- lots of temporary files (.log, .dvi, etc) get left around. need to somehow
  tell python to exit cleanly at the end, and maybe also use a different
  temporary directory.
- an array of tuples doesn't seem to get converted correctly? eg,
  zip(1:10, 1:10)
- create native "PyxGraph", "PyxCanvas" types
- integration of SVG renders into, eg, Jupyter. Python3 only.
- python2 vs. python3 versions of PyX