library/library_app/models/res_partner.py

from odoo import fields, models


class Partner(models.Model):
    _inherit = 'res.partner'
    published_book_ids = fields.One2many(
        'library.book',
        'publisher_id',
        string='Published Books'
    )

    book_ids = fields.Many2many(
        'library.book',
        string='Authored Books'
    )