In proyects, in every task i have a "total float field", and i need to sum the totals of tasks and render it in the project view, but only the tasks that are in the stage "To do".

this is my code, but is not working.

@api.depends('tasks.sum_total_cost')
    def todo_sum(self):
        todo = self.env['project.task'].search([('stage_id', '=', 'To Do')])
        for task in todo:
            task.sum_todo= round(sum(task.mapped('sum_total_cost')), 2)