The Python Desktop Server can be extended with macros that, for example, can repair broken RSS feeds. This is a feature that was added in version 0.2.6. An example is the repair of the Dotcomtod feed at http://dotcomtod.de/backend.php - it has quite a number of bugs. The macro for this is here: "DotComTod is pretty broken when it comes to RSS".
The main problems with the feed lie in incorrect encoding of umlauts and special characters, which causes most XML parsers to either refuse to cooperate or, like the Python Desktop Server, simply produce strange results.
Another application is simpler: many feeds have no GUID, but use the link tag on the item for the same purpose. For example, Tagesschau and Telepolis. Now many of these feeds have the problem that articles are edited later - then there are problems because the articles keep reappearing in the aggregator. The following macro fixes this: "the link of an item is entered as a guid". This transfers the link to the GUID and the Python Desktop Server then uses this to identify articles that have already been seen.