====== How to render large dot files ======
  * sfdp -x  -Tpng decix.fw.dot -o graph1.png
  * sfdp -x -Goverlap=scale -Tpng decix.fw.dot -o graph1.png
  * neato -x -Goverlap=scale -Tpng decix.fw.dot -o graph1.png
  * dot -Ksfdp -Tpng decix.fw.dot -o graph1.png
  * digraph foo { graph [splines=true overlap=false];
  * neato -Goverlap=scale -Tsvg mid.dot -o mid.svg