docs: private static String getCellTypeName(CellType cellType) {
      switch (cellType) {
        case BLANK:   return "blank";
        case STRING:  return "text";
        case BOOLEAN: return "boolean";
        case ERROR:   return "error";
        case NUMERIC: return "numeric";
        case FORMULA: return "formula";
      }
      return "#unknown cell type (" + cellType + ")#";
    }