MountSlot

One chassis mount point. Returned by: self.modules() on Rover / Pioneer (and drones expose analogous slots).

Member	Returns	Meaning
.index	number	Slot position on the chassis, 0-indexed; pass to mount / unmount
.type	string	Which modules fit: "nav", "sonar_basic", "drill_basic", "universal", "thruster", or "drone_module"
.module_id	string or None	Currently mounted module id, or None if empty
.internal_count	number	Internal slots this mounted module exposes (0 for non-containers)
.internal_items	list	Item ids installed in the module’s internal slots; None entries mark empty bays

Call before mount(...) / install(...) to find an empty compatible target.