library/my_library/models/library_book.py

# -*- coding: utf-8 -*-
from odoo import models, fields


class LibraryBook(models.Model):
    _name = 'library.book'
    _inherit = ['mail.thread', 'mail.activity.mixin']
    _description = 'Library Book'

    name = fields.Char('Title', required=True, track_visibility='onchange')
    date_release = fields.Date('Release Date', track_visibility='onchange')
    author_ids = fields.Many2many('res.partner', string='Authors', track_visibility='onchange')
    state = fields.Selection(
        [('draft', 'Not Available'),
         ('available', 'Available'),
         ('lost', 'Lost')],
        'State', default="draft", track_visibility='always')
    color = fields.Integer(track_visibility='onchange')

    def make_available(self):
        self.write({'state': 'available'})
        return True

    def make_lost(self):
        self.write({'state': 'lost'})
        return True