code: public static STextualDS getTextualDSForNode(SNode node, SDocumentGraph graph)
    {
      if (node != null)
      {
        List<DataSourceSequence> dataSources = graph.getOverlappedDataSourceSequence(
          node,
          SALT_TYPE.STEXT_OVERLAPPING_RELATION);
        if (dataSources != null)
        {
          for (DataSourceSequence seq : dataSources)
          {
            if (seq.getDataSource() instanceof STextualDS)
            {
              return (STextualDS) seq.getDataSource();
            }
          }
        }
      }
      return null;
    }
docs: Finds the {@link STextualDS} for a given node. The node must dominate a
  token of this text.
  
  @param node
  @return