code: def transition(trname='', field='', check=None, before=None, after=None):
      
      if is_callable(trname):
          raise ValueError(
              "The @transition decorator should be called as "
              "@transition(['transition_name'], **kwargs)")
      if check or before or after:
          warnings.warn(
              "The use of check=, before= and after= in @transition decorators is "
              "deprecated in favor of @transition_check, @before_transition and "
              "@after_transition decorators.",
              DeprecationWarning,
              stacklevel=2)
      return TransitionWrapper(trname, field=field, check=check, before=before, after=after)
docs: Decorator to declare a function as a transition implementation.