code: public static Session getJcrSession(final FedoraSession session) {
          if (session instanceof FedoraSessionImpl) {
              return ((FedoraSessionImpl)session).getJcrSession();
          }
          throw new ClassCastException("FedoraSession is not a " + FedoraSessionImpl.class.getCanonicalName());
      }
docs: Get the internal JCR session from an existing FedoraSession
  @param session the FedoraSession
  @return the JCR session