def labels
      @labels ||= workbook.defined_names.map do |name, label|
        [
          name,
          [label.row, label.col, label.sheet]
        ]
      end
    end
def labels
      @labels ||= workbook.defined_names.map do |name, label|
        [
          name,
          [label.row, label.col, label.sheet]
        ]
      end
    end
Returns an array which all labels. Each element is an array with
 [labelname, [row,col,sheetname]]