# File lib/docker/image.rb, line 155
    def save(names, filename = nil, conn = Docker.connection)
      if filename
        File.open(filename, 'wb') do |file|
          save_stream(names, {}, conn, &response_block_for_save(file))
        end
        nil
      else
        string = ''
        save_stream(names, {}, conn, &response_block_for_save(string))
        string
      end
    end