<xpath expr="//field[@name='partner_id']" position="replace">
<field string="Customer" name="partner_id" on_change="onchange_partner_id(type,partner_id,date_invoice,payment_term, partner_bank_id,company_id)" context="{'search_default_customer': 1}"/>
</xpath>
<xpath expr="//field[@name='partner_id']" position="replace">
<field string="Customer" name="partner_id" on_change="onchange_partner_id(type,partner_id,date_invoice,payment_term, partner_bank_id,company_id)" context="{'search_default_customer': 1}"/>
</xpath>