Host block-table record name for this xref.
Unique session id (e.g. xref-1).
OptionalinsertHost INSERT object id, when an INSERT was created.
Overlay id returned by AcApDocManager.loadOverlay.
Source file path or name used for display.
Whether the overlay geometry is currently visible.
One loaded external-reference display session.
Host document owns only xref metadata (BTR + INSERT). Geometry lives in a read-only secondary database and an overlay layout that is not registered in AcTrScene's editable layout map.