var writer = require('./')
var ws = writer(write, flush)
ws.on('finish', function () {
  console.log('finished')
})
ws.write('hello')
ws.write('world')
ws.end()
function write (data, enc, cb) {
  // i am your normal ._write method
  console.log('writing', data.toString())
  cb()
}
function flush (cb) {
  // i am called before finish is emitted
  setTimeout(cb, 1000) // wait 1 sec
}