* @param moduleName
   * @param environment
   * @return PlIterator
   */
  public static PlIterator sGetConceptInstances(String conceptName, String moduleName, Environment environment) {
    { Context module = PLI.safelyGetModule(moduleName, environment);
      Stella_Object concept = PLI.safelyGetConcept(conceptName, ((Module)(module)), environment);

      if (concept != null) {
        return (PLI.getConceptInstances(((LogicObject)(concept)), ((Module)(module)), environment));
      }
      else {
        return (PLI.EMPTY_PL_ITERATOR);
      }
    }
  }