def post_call(self, ctxt, result, action, post_mod, pre_mod):
return result<EOL>
A modifier hook function.  This is called in reverse-priority
order after invoking the ``Action`` for the step.  This allows
a modifier to inspect or alter the result of the step.

:param ctxt: The context object.
:param result: The result of the action.  This will be a
               ``StepResult`` object.
:param action: The action that was performed.
:param post_mod: A list of modifiers following this modifier
                 in the list of modifiers that is applicable
                 to the action.  This list is in priority
                 order.
:param pre_mod: A list of modifiers preceding this modifier in
                the list of modifiers that is applicable to
                the action.  This list is in priority order.

:returns: The result for the action, optionally modified.  If
          the result is not modified, ``result`` must be
          returned unchanged.  The default implementation of
          this method does so.