code: function run (x, cb) {
    const s = speculum(null, Echo, x)
    s.on('end', cb)
    s.on('error', cb)
  
    const reader = new Count({ highWaterMark: 0 }, 10)
  
    reader.pipe(s).resume()
  }
docs: Leverage x streams to transform, delayed echoing in this example, data from our readable stream.