code: private Set<String> getLinkTargetObjIDs(FieldDefinition linkDef, DBObjectBatch dbObjBatch) {
          Set<String> targObjIDs = new HashSet<>();
          for (DBObject dbObj : dbObjBatch.getObjects()) {
              List<String> objIDs = dbObj.getFieldValues(linkDef.getName());
              if (objIDs != null) {
                  targObjIDs.addAll(objIDs);
              }
              Set<String> removeIDs = dbObj.getRemoveValues(linkDef.getName());
              if (removeIDs != null) {
                  targObjIDs.addAll(removeIDs);
              }
          }
          return targObjIDs;
      }
docs: Target object IDs can be in the add or remove set.