Module sandbox

Graphviz DOT Language editing support.

L{Graphviz<http://graphviz.org/>} is a high quality open source
program to automatically layout directed and undirected graphs from a
text description of the node and edge relationships.  The description
language is called L{DOT<http://graphviz.org/doc/info/lang.html>} and
in most cases is generated by a program.  It is rare to write one by
hand, but when you have to, this mode is helpful.