I have two models:

class 1st_model(models.Model):  
 
    scode =  fields.Char('Code', size=3) 
    
    field_to_update = fields.Char('Updated')

and

class 2nd_model(models.Model):
 
    _inherits = {'1st_model': 'id_1st_model'} 
    id_1st_model = fields.Many2one('1st_model', 'Code', widget="many2one_list")
 
    name =  fields.Char(string='Name', size=100, required=True)  
     
    def update_field_to_update(self, cr, uid, ids, context=None):
        context = context or {}
        assignment_obj = self.pool.get('1st_model')
        for record in self.browse(cr, uid, ids, context=context):
            if record.id_1st_model:
                assignment_ids = assignment_obj.search(cr, uid, [('id_1st_model', '=', record.id_1st_model)], context=context)
                if assignment_ids:
                    assignment_obj.write(cr, uid, assignment_ids, {'field_to_update': 'ok'}, context=context)
        return True

When I create a new entry in 2nd_model, I would like to wite 'ok' in 'field_to_update' of 1st_model. But this code doesn't work.

Any idea?