Get a list of uncontained assets for a given asset type. Uncontained assets are assets that are not contained within another asset, meaning they are at the top level of their hierarchy. They could be:

* A source asset that represents an external system, such as a database, from which assets are synced to Alation for cataloging.
* A top-level native Alation asset, such as a Document Hub.

Assets that aren't in a hierarchy at all won't return a response.