Used for places queries and as a base for bookmark folders.
Note that if you request places to not be expanded in the options that
generated this node, this item will report it has no children and never try
to populate itself.
Get the queries which build this node’s children.
Only valid for RESULT_TYPE_QUERY nodes.
Get the options which group this node’s children.
Only valid for RESULT_TYPE_QUERY nodes.
For both simple folder nodes and simple-folder-query nodes, this is set
to the concrete itemId of the folder. Otherwise, this is set to -1.