This read-only object mirrors the `id` property of a physical I/O expander module -- an add-on board that gives a blade or compute node extra mezzanine/PCIe ports inside Cisco UCS Manager's internal information model, exposed here as a non-negative gauge value for this I/O expander instance. The id is a small numeric identifier distinguishing this specific instance of this I/O expander instance from its siblings under the same parent (e.g., LED 1 vs LED 2 on the same board). On a chassis with two IOEs installed you would see id=1 and id=2 in separate rows for the IOE plugged into slot 2 of a UCS X210c compute node, letting you tell them apart even though both share the same parent dn prefix.