code: public void setSubContexts(String[] subContextOf) {
          if (subContextOf == null) {
              this.subContexts = StringUtils.EMPTY_STRING_ARRAY;
          } else {
              ProtempaUtil.checkArrayForNullElement(subContextOf, 
                      "subContextOf");
              ProtempaUtil.checkArrayForDuplicates(subContextOf, "subContextOf");
              this.subContexts = subContextOf.clone();
          }
      }
docs: Sets the ids of other context definitions that, together with this one,
  have a specific meaning when their intervals intersect.
  
  @param subContextOf an array of context proposition ids.