/**
* Refund a payment.
* Available $params are:
* - amount: The amount to refund. The amount must not exceed the maximum
* amount of Payment. Can be used for partial refunds. If ommited
* then a full refund will be created. [Optional]
* - description: A description for this refund max 255 chars. [Optional]
*
* @param string|stdClass $token A valid payment token returned from a
* successful payment creation.
* @param array $params
*/
public static function refund($token, array $params = array())
{
$params['token_id'] = $token;
return parent::invoke(__FUNCTION__, static::RESOURCE_NAME, $params);
}