protected function getWriteableAttributes()
{
return array('coupon_code', 'name', 'discount_type', 'redeem_by_date', 'single_use', 'applies_for_months', 'duration', 'temporal_unit', 'temporal_amount', 'max_redemptions', 'applies_to_all_plans', 'discount_percent', 'discount_in_cents', 'plan_codes', 'hosted_description', 'invoice_description', 'applies_to_non_plan_charges', 'redemption_resource', 'max_redemptions_per_account', 'coupon_type', 'unique_code_template', 'unique_coupon_codes', 'discount_type', 'free_trial_amount', 'free_trial_unit');
}