A collection of UtilityAssetType objects which specifies what to include in the trace results. Only elements that belong to this UtilityAssetType are included in the trace result. This property is independent of asset types in the UtilityTraceConfiguration.filter. This is applied after all other tracing calculations, including traversal, filters, and function calculation. If this is empty and UtilityTraceConfiguration.outputCondition is null, all elements are returned. Otherwise, elements which match either of these criteria are returned.