def each
      bucket.keys do |keys|
        keys.each do |key|
          if x = self[key]
            yield x
          end
        end
      end
    end
def each
      bucket.keys do |keys|
        keys.each do |key|
          if x = self[key]
            yield x
          end
        end
      end
    end
Iterate over all items using key streaming.