def delete_security_group_rule(self, context, group_id, rule):
raise NotImplementedError('<STR_LIT>'<EOL>'<STR_LIT>')<EOL>
Delete a security group rule.

        :raises NotImplementedError: This driver does not implement security
                                     groups.

        NOTE: Security groups will be supported in the future, but for now
        they are explicitly disallowed.