def _purge_orphaned_workflow_executions(self):
        """
        Purge workflow executions that are idled and orphaned.
        """
        try:
            purge_orphaned_workflow_executions(logger=LOG)
        except Exception as e:
            LOG.exception(
                "Failed to purge orphaned workflow executions: %s" % (six.text_type(e))
            )

        return True

        Purge workflow executions that are idled and orphaned.
        
st2reactor/st2reactor/garbage_collector/base.py