def sheet_by_name(name)
      index = @worksheets.index { |sheet| sheet.name == name }
      @worksheets[index] if index
    end
def sheet_by_name(name)
      index = @worksheets.index { |sheet| sheet.name == name }
      @worksheets[index] if index
    end
A quick helper to retrive a worksheet by name
 @param [String] name The name of the sheet you are looking for
 @return [Worksheet] The sheet found, or nil