docs: @CheckForNull
      public String getNextNodeId( @Nonnull final String nodeId ) throws IllegalArgumentException {
          final int idx = indexOf( nodeId );
          if ( idx < 0 ) {
              throw new IllegalArgumentException( "The given node id "+ nodeId +" is not part of this list " + toString() );
          }
          if ( size() == 1 ) {
              return null;
          }
          return ( idx == size() - 1 ) ? get( 0 ) : get( idx + 1 );
      }