anchor.diff:  
   renders as:
   
  -[graphviz]
  +[graphviz,_images/graphviz-demo,png]
   ----
   digraph automata_0 {
     size ="8.5, 11";
  
positive.code: 
  renders as:
  
  [ditaa]
  ----
      +--------+   +-------+    +-------+
      |        | --+ ditaa +--> |       |
  
negative.code: For example:
  
  ....
  [plantuml,_images/plantuml-demo,png]
  --
  class Car
  
  