class custom_maintenance_notify(models.Model):
    _name = MaintenanceRequest
    _inherit = ['maintenance.request','mail.thread']

    @api.model
    def create(self, vals):
        record = super(MaintenanceRequest, self).create(vals)

        template_id = self.env.ref('custom_maintenance.new_request_template').id
        if template_id:
            record.message_post_with_template(template_id)
        return record