一般情况下，Odoo 中 many2many 对象见的关系由odoo自动维护，如果我们通过 code 向Many2many 关系对象添加数据，怎么实现呢？举例说明:首先定义字段如下：
user_rel_ids = fields.Many2many(comodel_name='course',relation='user_course_rel',column1='user_id', column2='course_id')
Oruser_rel_id = fields.Many2many('course')
然后使用下面的语句添加关系：
user_rel_id = (4,[course_ids])
参数说明如下：
(0, 0, { values }) link to a new record that needs to be created with the given values dictionary
(1, ID, { values }) update the linked record with id = ID (write values on it)
(2, ID) remove and delete the linked record with id = ID (calls unlink on ID, that will delete the object completely, and the link to it as well)
(3, ID) cut the link to the linked record with id = ID (delete the relationship between the two objects but does not delete the target object itself)
(4, ID) link to existing record with id = ID (adds a relationship)
(5) unlink all (like using (3,ID) for all linked records)
(6, 0, [IDs]) replace the list of linked IDs (like using (5) then (4,ID) for each ID in the list of IDs)
来源：苏州远鼎官网
