code: private static String propositionId(Instance extendedProposition) {
          Instance proposition = (Instance) extendedProposition
                  .getOwnSlotValue(extendedProposition.getKnowledgeBase()
                  .getSlot("proposition"));
          if (proposition.hasType(proposition.getKnowledgeBase().getCls(
                  "ConstantParameter"))) {
              throw new IllegalStateException(
                      "Constant parameters are not yet supported as "
                      + "components of a high level abstraction definition.");
          } else {
              return proposition.getName();
          }
      }
docs: Returns the proposition id for an extended proposition definition.
  
  @param extendedProposition an ExtendedProposition.
  @return a proposition id {@link String}.