def uniq(&blk)
      if block_given?
        Thresholds.new(@thresholds.uniq(&blk))
      else
        Thresholds.new(@thresholds.uniq{ |lineitem| lineitem.to_s(true) })
      end
    end
def uniq(&blk)
      if block_given?
        Thresholds.new(@thresholds.uniq(&blk))
      else
        Thresholds.new(@thresholds.uniq{ |lineitem| lineitem.to_s(true) })
      end
    end
Uniques by default to printable output
 Returns a new Threshold Object