Magento中Mage_Catalog_Model_Product的函数getDownloadableData和setDownloadableData在哪里实现

I want to modify the Downloadable Information / Links of a product programmability.

I am able to create a downloadable product. But I can't find how to edit the links.

I think the fonction setDownloadableData / getDownloadableData could help me.

But, i can't find them in the Magento source (1.7.0.2).

with

grep -r "setDownloadableData" magento/*

I can only see the call to the function. Not the implementation. ...

    /magento/app/code/core/Mage/Downloadable/Model/Link/Api.php
$product->setDownloadableData($downloadable);
    /magento/app/code/core/Mage/Downloadable/Model/Observer.php
$product->setDownloadableData($downloadable);

The answer is Varien Data Collections

http://www.magentocommerce.com/knowledge-base/entry/magento-for-dev-part-8-varien-data-collections

You cannot find the methods because they don't exist.
Most of the classes in Magento extend Varian_Object class that overloads the 'magic method' __call. This is called when a method in the class does not exist.
To get a better view on this take a look at Varien_Object::__call(), this article and what php.net has to say about overloading