def _get_referenced_action_model(self, action_ref):
        """
        Return Action object for the action referenced in a rule.

        :param action_ref: Action reference.
        :type action_ref: ``str``

        :rtype: ``ActionDB``
        """
        # NOTE: We need to retrieve pack and name since that's needed for the PK
        action_dbs = Action.query(
            only_fields=["pack", "ref", "name", "parameters"], ref=action_ref, limit=1
        )

        if action_dbs:
            return action_dbs[0]

        return None

        Return Action object for the action referenced in a rule.

        :param action_ref: Action reference.
        :type action_ref: ``str``

        :rtype: ``ActionDB``
        
st2common/st2common/models/db/rule.py