docs: private synchronized Constructor getIndirectionHandlerConstructor()
      {
          if(_indirectionHandlerConstructor == null)
          {
              Class[] paramType = {PBKey.class, Identity.class};
  
              try
              {
                  _indirectionHandlerConstructor = getIndirectionHandlerClass().getConstructor(paramType);
              }
              catch(NoSuchMethodException ex)
              {
                  throw new MetadataException("The class "
                          + _indirectionHandlerClass.getName()
                          + " specified for IndirectionHandlerClass"
                          + " is required to have a public constructor with signature ("
                          + PBKey.class.getName()
                          + ", "
                          + Identity.class.getName()
                          + ").");
              }
          }
          return _indirectionHandlerConstructor;
      }