def create_or_find_format_by name, variant=:default
      fs = @formats[name]
      fs = @formats[name] = {} if fs.nil?
      f = fs[variant]
      if f.nil?
        f = Workbook::Format.new
        if variant != :default and fs[:default]
          f = fs[:default].clone
        end
        @formats[name][variant] = f
      end
      return @formats[name][variant]
    end
def create_or_find_format_by name, variant=:default
      fs = @formats[name]
      fs = @formats[name] = {} if fs.nil?
      f = fs[variant]
      if f.nil?
        f = Workbook::Format.new
        if variant != :default and fs[:default]
          f = fs[:default].clone
        end
        @formats[name][variant] = f
      end
      return @formats[name][variant]
    end
Create or find a format by name
 @return [Workbook::Format] The new or found format
 @param [String] name of the format (e.g. whatever you want, in diff names such as 'destroyed', 'updated' and 'created' are being used)
 @param [Symbol] variant can also be a strftime formatting string (e.g. "%Y-%m-%d")