I couldn't find any docs on this but I guess I'm trying to find something similar to the DataObject::get($obj, $filter, $sort, $join, $limit) method. If there is documentation, can you pls. provide the url?
Yer, this is one of those 'hidden Gems'. I don't think it is documented.
But it is important to note that this returns a [url=http://doc.silverstripe.org/doku.php?id=componentset]ComponentSet[/url] not a [url=http://doc.silverstripe.org/doku.php?id=dataobjectset]DataObjectSet[/url]
PS: it is hinted at here: http://doc.silverstripe.org/doku.php?id=datamodel#custom_relation_getters