code: private String getText(SNode node, VisualizerInput input)
    {
      SDocumentGraph sDocumentGraph = input.getSResult().getDocumentGraph();
  
      List<DataSourceSequence> sequences = sDocumentGraph.
        getOverlappedDataSourceSequence(node, SALT_TYPE.STEXT_OVERLAPPING_RELATION);
  
      if (sequences != null && sequences.size() > 0)
      {
        return ((STextualDS) sequences.get(0).getDataSource()).getText().
          substring(sequences.get(0).getStart().intValue(), sequences.get(0).getEnd().intValue());
      }
  
      return "";
    }
docs: Get the text which is overlapped by the SNode.
  
  @return Empty string, if there are no token overlapped by the node.