Relation pm#sub_collection_of (collection,collection)  DO NOT use this type; it only exists because the SUMO does not respect common reading conventions of parameters
  supertype:  relation_between_collections
  subtype:  sub_collection__subcollection__sub_collection_of (collection,collection)  the 1st collection is a proper part of the 2nd
  subtype:  sub_list__sublist__sub_list_of (list,list)  the 1st argument is a sublist of the 2nd, i.e. every element of the 1st is an element of the 2nd and the elements that are common to both lists have the same order in both lists
     subtype:  initial_list__initiallist (list,list)  the 1st argument (?L1) is a sublist of the 2nd (?L2), and (sumo#list_order_fn ?L1 ?NUMBER) returns the same value as (sumo#list_order_fn ?L2 ?N) for all of the values of ?N over which (sumo#list_order_fn ?L1 ?N) is defined
  subtype:  final_segment_of__finalsegmentof (collection,collection)  USE pm#final_segment INSTEAD
     subtype:  sublist__final_segment_of__finalsegmentof (list,list)  USE pm#final_segment INSTEAD OF THIS RELATION TYPE; "sublist" is a misleading name; "final_segment_of" is better