You are writing a Python script that uses RESTCONF against an IOS XE device to retrieve the running OSPF configuration. The OSPF container has deeply nested areas, networks, and interface sub-elements, but for a quick dashboard you only need the top-level OSPF process IDs and their router-id — not the full nested tree. Retrieving the entire subtree is slow and returns megabytes of JSON. Which RESTCONF query parameter should you add to the GET request to limit how many levels of nested descendants are returned?