code: public function start($msg = null, array $extraInfo = [])
      {
          if ($this->status != self::NOT_STARTED) {
              throw new TrackerException("Cannot start tracker that was already started");
          }
  
          $this->status = self::RUNNING;
          $this->startTime = microtime(true);
  
          $tick = new Tick($this, Tick::SUCCESS, $msg, $extraInfo, 0);
          $this->dispatcher->dispatch(Events::TRACKER_START, $tick);
          $this->lastTick = $tick;
      }
docs: Start processing
  
  If this method is not called explicitely, it will automatically
  be called upon first tick
  
  @param string $msg Optional message to include
  @param array  $extraInfo