Returns the occupancy trends lines configured on a single camera.

Lines are grouped by line preset. Each preset includes the object class it
counts and the lines drawn on the camera frame, with each line's counted
direction and its start and end points. Point coordinates are normalized to
the frame dimensions, from 0 to 1.

The preset_id of each preset can be passed to the occupancy trends data
endpoint to retrieve the counts for that preset. A camera with no lines
configured returns an empty presets list.