vertical-cooperative/easy_my_coop_fr/models/partner.py

from odoo import fields, models


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

    legal_form = fields.Selection(selection_add=[
                            ('asso', 'Association'),
                            ('eurl', 'EURL / Entreprise individuelle'),
                            ('sarl', 'SARL'),
                            ('sa', 'SA / SAS')
                            ])