如何应用域过滤器以使“任务中的阶段”明智地出现？

Question

我正在尝试进行部门明智的项目阶段。默认情况下，任务阶段是根据项目生成的。

我这样做是为了为部门和阶段添加Many2many关系。

 class DepartmentStages(models.Model):
    _inherit = 'project.task.type'

    department_ids = fields.Many2many(comodel_name='hr.department',
        relation='hr_department_project_task_type_rel',
        column1='project_task_type_id',
        column2='hr_department_id', string='Departments')

此外，我在stages_ids中添加了hr.department。

class HrDepartmentInherit(models.Model):
    _inherit = 'hr.department'

    stage_ids = fields.Many2many(comodel_name='project.task.type',
        relation='hr_department_project_task_type_rel',
        column1='hr_department_id',
        column2='project_task_type_id',
        string='Tasks Stages')

我在department_id中添加了project.project字段。

class ProjectProjectInhert(models.Model):
    _inherit = 'project.project'

    department_id = fields.Many2one(
        comodel_name='hr.department',
        default=_get_department,
        string='Department')

    @api.multi
    def _get_department(self):
        emp_model = self.env['hr.employee']
        department_id = False
        employee = emp_model.search([('user_id', '=', self.env.uid)], limit=1)
        if employee and employee.department_id:
            department_id = employee.department_id.id
        return department_id 

要在stage_id中获得project.task，我已经继承了如下字段：

class ProjectTaskInherit(models.Model):
    _inherit = 'project.task'

    stage_id = fields.Many2one(comodel_name='project.task.type', string='Stage',
        track_visibility='onchange', domain="[('department_ids', '=', project_id.department_id)]")

这显示Uncaught Error: AttributeError: object has no attribute 'department_id'。

那么，我该如何应用域过滤器以使部门部门明智？ 预先谢谢你。