Is it possible to get default recipients when sending mail (Actually , only Administrator is shown) ?

def action_send(self):
        mail_template = self.env.ref('hr_test.my_email_template')
        mail_template.send_mail(self.id, force_send=True)

        partners = []
        if self.applicant_id and self.applicant_id.user_id:
            partners.append(self.applicant_id.user_id.partner_id.id)
        partners = partners + [user.partner_id.id for user in
                               self.env.ref('hr_training.training_officer').users if
                               user.partner_id.id not in partners]
        for rec in self:
            if rec.applicant_id and rec.applicant_id.parent_id:
                parent = rec.applicant_id.parent_id
                if parent.user_id and parent.user_id.partner_id.id not in partners:
                    partners.append(parent.user_id.partner_id.id)

        for partner in partners:
            mail_template.send_mail(self.id, force_send=True,
            raise_exception=True,
            email_values={'email_to': partner})