class Missions(models.Model):

    _name = 'mission.mission'
    _description = 'mission.mission'

    _rec_name = 'mission_id'

    project_ids = fields.Many2one('project.project', string='Projet')
    mission_id = fields.Many2one('missname.missname', String='Mission')
    miss_id = fields.Integer(string='I_mission')
    version = fields.Selection([('pro', 'Provisoire'), ('Déf', 'Définitif')])
    Délais_jrs = fields.Float(string='Délai en jours', compute='_compute_delai_mois')
    Délais_mois = fields.Integer(string='Délai en mois')
    ordre_arre = fields.Date(string='Ordre d arrét')
    ordre_repr = fields.Date(string='Ordre de reprise')
    Délai_restants = fields.Float(string='Délai Restant en mois', compute='_compute_delais_restant')
    Délai_écoulée = fields.Float(string='Délai écoulé en mois', compute='_compute_delais_ecoule')
    date_debut = fields.Date(string='Date de la mission')
    nbr_mission = fields.Float(string='nombre de mission', compute='_delais_mission')


    def _delais_mission(self):
        for k in self:

            if k.ordre_arre and k.ordre_repr:
                date_1 = datetime.strptime(k.ordre_arre, '%Y-%m-%d')
                date_2 = datetime.strptime(k.ordre_repr, '%Y-%m-%d')
                k.nbr_mission = ((date_2 - date_1).days) / 30
                print(k.nbr_mission)




class Delais(models.Model):

    _name = 'delais.delais'
    _descritpion = 'delais.delais'

    _rec_name = 'project_ids'

    project_ids = fields.Many2one('project.project', string='Projet')
   delai_arr_mois = fields.Float(string='Délais D arrét en mois', compute='_delai_mission')
@api.multi
def _delai_mission(self):
     #domaine = ['project_ids', '=', self.project_ids]
     dict = self.env['mission.mission'].search_read([['project_ids', '=', self.project_ids], ['nbr_mission']])

     print(dict)
     somme = 0
     for key in dict:
         print(key['nbr_mission'])
         somme = somme + key['nbr_mission']
         print(f'la somme est : {somme}')
         self.delai_arr_mois = somme

help please !!