How to use the readable-stream.PassThrough.call function in readable-stream

function Clone (parent, opts) {
  if (!(this instanceof Clone)) {
    return new Clone(parent, opts)
  }

  var objectMode = parent._readableState.objectMode

  opts = opts || {}
  opts.objectMode = objectMode

  this.parent = parent

  PassThrough.call(this, opts)

  forwardDestroy(parent, this)

  parent.pipe(this)

  // the events added by the clone should not count
  // for starting the flow
  // so we add the newListener handle after we are done
  this.on('newListener', onDataClone)
  this.on('resume', onResumeClone)
}

function Job (printer, req) {
  PassThrough.call(this)

  var attributes = utils.getAttributesForGroup(req._body, C.OPERATION_ATTRIBUTES_TAG)
  this.compression = utils.getFirstValueForName(attributes, 'compression')

  this._printer = printer
  this._req = req

  this.id = ++printer._jobId
  this.state = C.JOB_PENDING
  this.uri = printer.uri + this.id
  this.name = utils.getFirstValueForName(attributes, 'job-name')
  this.userName = utils.getFirstValueForName(attributes, 'requesting-user-name')
  this.createdAt = new Date()

  printer.add(this)
}

function Cloneable (stream, opts) {
  if (!(this instanceof Cloneable)) {
    return new Cloneable(stream, opts)
  }

  var objectMode = stream._readableState.objectMode
  this._original = stream
  this._clonesCount = 1

  opts = opts || {}
  opts.objectMode = objectMode

  PassThrough.call(this, opts)

  forwardDestroy(stream, this)

  this.on('newListener', onData)
  this.once('resume', onResume)

  this._hasListener = true
}

var Source = function (self, offset) {
  this._parent = self
  this.offset = offset
  PassThrough.call(this)
}

var Source = function (self, offset) {
  this._parent = self
  this.offset = offset
  PassThrough.call(this)
}

function Cloneable (stream, opts) {
  if (!(this instanceof Cloneable)) {
    return new Cloneable(stream, opts)
  }

  var objectMode = stream._readableState.objectMode
  this._original = stream
  this._clonesCount = 1

  opts = opts || {}
  opts.objectMode = objectMode

  PassThrough.call(this, opts)

  forwardDestroy(stream, this)

  this.on('newListener', onData)
  this.once('resume', onResume)

  this._hasListener = true
}

function GenericWriteChannel() {
  if (!(this instanceof GenericWriteChannel)) {
    return new GenericWriteChannel();
  }
  PassThrough.call(this, { objectMode: true, highWaterMark: 16 });
}

function GenericReadChannel() {
  if (!(this instanceof GenericReadChannel)) {
    return new GenericReadChannel();
  }
  PassThrough.call(this, { objectMode: true, highWaterMark: 16 });
}

var Source = function (self, offset) {
  this._parent = self
  this.offset = offset
  PassThrough.call(this)
}

var Source = function (self, offset) {
  this._parent = self
  this.offset = offset
  PassThrough.call(this)
}