Hello,
I am new to odoo

@api.model
def test_cron_job(self):
    print("abcddddddddddddddddddddddddddddddddddddddddddd")
    today = fields.Date.today()
    custom_date = self.env['hr.holidays'].search([('custom_date_from', '>=', today)])
    print("custom_date", custom_date)
    for rec in custom_date:
        if rec.custom_date_from - today == 7:
            mail = self.env['mail.template'].search(['hr_holidays.leave_email_template'])
            mail.send()
        else:
          if rec.custom_date_from - today == 1:
            mail = self.env['mail.template'].search([('hr_holidays.leave_request_email_template')])
            mail.send()

I am getting this error

Traceback (most recent call last):
  File "/opt/odoo/odoo11/odoo/tools/safe_eval.py", line 351, in safe_eval
    return unsafe_eval(c, globals_dict, locals_dict)
  File "", line 1, in 
  File "/opt/odoo/sintranet-SintraNet_Prod/half_day_leave/models/custom_hr_holidays.py", line 54, in test_cron_job
    if rec.custom_date_from - today == 7:
TypeError: unsupported operand type(s) for -: 'str' and 'str'