i m beginner in odoo and I have form like below and i want to add a label of the two groups

<form string="New Expedition">
    <sheet>
        <group>
            <group>
                <field name="sender_name"/>
                <field name="sender_lastname"/>
                <field name="sender_phone"/>
                <field name="sender_identity"/>
                <field name="sender_city"/>
                <field name="sender_address"/>
            </group>
            <group>
                <field name="receiver_name"/>
                <field name="receiver_lastname"/>
                <field name="receiver_phone"/>
                <field name="receiver_identity"/>
                <field name="receiver_city"/>
                <field name="receiver_address"/>
            </group>
        </group>
        <footer>
            <button name="submit" type="object" string="Submit" class="oe_right oe_button_box"/>
        </footer>
    </sheet>
</form>