code: def decorate_postinject(func, classkey=None, skipmain=False):
      
      #import utool as ut
      global __CLASSTYPE_POSTINJECT_FUNCS__
      assert classkey is not None, 'must specify classkey'
      #if not (skipmain and ut.get_caller_modname() == '__main__'):
      __CLASSTYPE_POSTINJECT_FUNCS__[classkey].append(func)
      return func
docs: Will perform func with argument self after inject_instance is called on classkey
  
      classkey is some identifying string, tuple, or object