def key
      if @key.nil?
        hash_key = @name.to_s
        @key = hash_key
        keys = @tags.keys
        keys.sort
        keys.each do |k|
          v = tags[k]
          hash_key += "|#{k}|#{v}"
        end
        @key = hash_key
      end
      @key
    end
def key
      if @key.nil?
        hash_key = @name.to_s
        @key = hash_key
        keys = @tags.keys
        keys.sort
        keys.each do |k|
          v = tags[k]
          hash_key += "|#{k}|#{v}"
        end
        @key = hash_key
      end
      @key
    end
lazyily compute a key to be used in hashes for efficiency