Hi guys I want to list some items. I have a many2one field to select a option and then I want to put a field to list the items of the selected option. How can I do that?

class gs_pet_apagar(osv.osv):

    _name = 'apagar.pets'
    _description = 'Apagar Pets'

    _columns = {

      'owner_id':fields.many2one('gs.owner','ID_owner'),
                }

gs_pet_apagar()

my xml

<?xml version="1.0" encoding="utf-8"?>

<openerp> <data>

<record id="apagar_pets_form" model="ir.ui.view">
        <field name="name">apagar.pets.form</field>
        <field name="model">apagar.pets</field>
        <field name="arch" type="xml">
            <form string="Apagar Pets" version="7.0">

                <group string="Lista de Pets" col="1">

            <field name="owner_id" widget="selection" string="Nome"/>

                </group>
            </form>
        </field>
    </record>



    <record id="gs_apagar_pets_act" model="ir.actions.act_window">
        <field name="name">Apagar Pets</field>
        <field name="type">ir.actions.act_window</field>
        <field name="res_model">apagar.pets</field>
        <field name="view_type">form</field>
        <field name="view_mode">form</field>
        <field name="target">new</field>
    </record>

   <menuitem
        name="Apagar Pets"
        parent="gs_owners"
        action="gs_apagar_pets_act"
        id="gs_apagar"
        sequence="0"/>

   </data>

</openerp>