Hi. Try to change value of the tag using odoo studio and dependensies. Here is my code.

for rec in self:

  if rec.x_studio_notification_date == rec.x_studio_next_pm_date  - dateutil.relativedelta.relativedelta(days=rec.x_studio_email_days_before_due_date):

   record['x_studio_pm_state']="PM Due"

I think this record['x_studio_pm_state']="PM Due" isn't a correct way to change value of the tag field. Any help is appreciatred as always