Campos en Odoo

product_cum_model.py

from odoo import models, fields


class ProductTemplate(models.Model):
    _inherit = "product.template"
    cum = fields.Char(
        'CUM Code', size=40
    )


class AccountInvoiceLine(models.Model):
    _inherit = "account.invoice.line"
    cum = fields.Char(string='CUM Code',
                      store=True,
                      related='product_id.cum')
    

product_cum_view.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <data>
        <!-- Imprimir en la factura, funciona bien -->
        <template id="report_invoice_document_cum" inherit_id="account.report_invoice_document">
            <xpath expr="//div[contains(@class, 'page')]/table[1]/thead/tr/th[2]" position="before">
                <th>CUM</th>
            </xpath>
            <xpath expr="//div[contains(@class, 'page')]/table[1]/tbody/tr/td[2]" position="before">
                <td>
                    <field name="l.cum"/>
                </td>
            </xpath>
        </template>
    </data>
</odoo>