partner-contact/partner_contact_gender/models/res_partner.py

# Copyright 2014-2015 Grupo ESOC <www.grupoesoc.es>
# Copyright 2017-Apertoso N.V. (<http://www.apertoso.be>)
# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).

from odoo import fields, models


class ResPartner(models.Model):
    _inherit = "res.partner"

    gender = fields.Selection(
        [("male", "Male"), ("female", "Female"), ("other", "Other")]
    )