Loading entities or instances into CzmlDataSource

I am using CzmlDatasources to group the objects in my scene so they can be added and removed.

According to the documentation you can produce entities using a CzmlDataSource, but when I try to load a circle I get an error saying:

“{“x”:6378137,“y”:6378137,“z”:6356752.314245179} is not a valid CZML interval.”

Is there a certain way they need to be prepared so that they will load correctly?

Also, is it possible to load a geometry instance into a CzmlDataSource? For example, can I load an EllipseOutlineGeometry instance into a data source?

Can you attach a small sample or link to the code where you’re initializing the CzmlDataSource object?