def padding
      last   = bytes.last
      subset = subset_padding

      if subset.all?{|e| e == last }
        self.class.new(subset)
      else
        self.class.new([])
      end
    end
def padding
      last   = bytes.last
      subset = subset_padding

      if subset.all?{|e| e == last }
        self.class.new(subset)
      else
        self.class.new([])
      end
    end
Return any existing padding