Hello i have a question how to set automatically value field nomor_faktur_po on purchase.order when i set value field nomor_faktur_sp on stock.picking with onchange?

class stock_nomor_faktur(models.Model):

    _inherit = 'stock.picking'

nomor_faktur_sp = fields.Char(string='Nomor Faktur')

class stock_nomor_faktur(models.Model):

    _inherit = 'purchase.order'

    nomor_faktur_po = fields.Char(string='Nomor Faktur')

      My stock.picking view

    <record id="nomor_faktur_stock_picking" model="ir.ui.view">

        <field name="name">nomor_faktur_stock_picking</field>

        <field name="model">stock.picking</field>

        <field name="inherit_id" ref="stock.view_picking_form"/>

        <field name="arch" type="xml">

            <xpath expr="//field[@name='origin']" position="after">

                <field name="nomor_faktur_sp"/>

            </xpath>

        </field>

    </record>

My purchase.order View

<record id="nomor_faktur_purchase_order" model="ir.ui.view">

        <field name="name">nomor_faktur_purchase_order</field>

        <field name="model">purchase.order</field>

        <field name="inherit_id" ref="purchase.purchase_order_form"/>

        <field name="arch" type="xml">

            <xpath expr="//field[@name='location_dest_id']" position="after">

                <field name="nomor_faktur_po"/>

            </xpath>

        </field>

    </record>