python-simplegeneric 0.8.1-1~ubuntu12.04.1 (amd64 binary) in ubuntu precise

 The simplegeneric module lets you define simple single-dispatch generic
 functions, akin to Python's built-in generic functions like len(), iter() and
 so on. However, instead of using specially-named methods, these generic
 functions use simple lookup tables, akin to those used by e.g. pickle.dump()
 and other generic functions found in the Python standard library.