src/TreeHouse/Domain/EventStream.php
public function track(EventStream $stream)
    {
        if (!in_array($stream, $this->tracking, true)) {
            $this->tracking[] = $stream;
        }
    }
public function track(EventStream $stream)
    {
        if (!in_array($stream, $this->tracking, true)) {
            $this->tracking[] = $stream;
        }
    }
public function track ( EventStream $ stream ) { if ( ! in_array ( $ stream , $ this -> tracking , true ) ) { $ this -> tracking [ ] = $ stream ; } }
When tracking, appended events are also appended to the tracking streams.

@param EventStream $stream
When tracking appended events are also appended to the tracking streams .