I created a custom app to add some fields to the project module (see code below).
I can succesfully load the app but when I open the project task I get the following error. How to resolve this?

-------- error -----------
AttributeError: 'project.task' object has no attribute '_compute_progress'

The above server error caused the following client error:

null

-------- code -----------

from odoo import fields, models, api

@api.depends("planned_effort", "realized", "kanban_state")

def _compute_progress(self):

    for record in self: 

        if record['kanban_state'] == 'done':

            record['progressed'] = 100

        elif record['planned_effort'] > 0: 

            record['progressed'] = round(record['realized'] / record['planned_effort'] * 100)

        else:

            record['progressed'] = 0

class ClassAdditionalFields(models.Model):

   _inherit = 'project.task'

   planned_effort = fields.Integer(string='Planned effort (hr)', default=1)

   realized = fields.Integer(string='Realized (hr)', default=0)

   progressed = fields.Integer(string='Task progress', compute="_compute_progress", readonly=True)