In code generation process, it is possible to have simple logic, e.g. filtering a list, in either of python scripts or Jinja template files.

To avoid moving them back-and-forth, we should have a simple guidance for code generators.
I think its main focus is under bindings/{templates,scripts}.

http://www.chromium.org/developers/design-documents/idl-build and http://www.chromium.org/developers/jinja can be a starting position?