def ref(self, xml_id):
        """Return the record corresponding to the given `xml_id` (also called
        external ID).
        Raise an :class:`RPCError <odoorpc.error.RPCError>` if no record
        is found.

        .. doctest::

            >>> odoo.env.ref('base.lang_en')
            Recordset('res.lang', [1])

        :return: a :class:`odoorpc.models.Model` instance (recordset)
        :raise: :class:`odoorpc.error.RPCError`
        """
        model, id_ = self._odoo.execute(
            'ir.model.data', 'xmlid_to_res_model_res_id', xml_id, True)
        return self[model].browse(id_)
Return the record corresponding to the given `xml_id` (also called
        external ID).
        Raise an :class:`RPCError <odoorpc.error.RPCError>` if no record
        is found.

        .. doctest::

            >>> odoo.env.ref('base.lang_en')
            Recordset('res.lang', [1])

        :return: a :class:`odoorpc.models.Model` instance (recordset)
        :raise: :class:`odoorpc.error.RPCError`