return null;
    }
    // figure out mode, and delimiters
    String delimModeStr = ctx.getValue("delimMode");
    DelimMode delimMode = DelimMode.EXCLUDE; // default to exclude mode
    if (delimModeStr != null) {
      if ("exclude".equals(delimModeStr)) {
        delimMode = DelimMode.EXCLUDE;
      } else if ("prev".equals(delimModeStr)) {
        delimMode = DelimMode.INCLUDE_PREV;