The ordered set of light ids from the lights which are in the group. This resource shall contain an array of at least one element with the exception of the “Room” type: The Room type may contain an empty lights array. Each element can appear only once. Order of lights on creation is preserved. A light id must be an existing light resource in /lights. If an invalid lights resource is given, error 7 shall be returned and the group is not created. There shall be no change in the lights.