code: public function registerFreeProcessId($pid) {
  		$processDetails = $this->getProcessDetails($pid);
  		if ($processDetails !== NULL) {
  			$this->registerFreeProcess($processDetails);
  		}
  
  		return $this;
  	}
docs: Register the ProcessDetails with the given PID as free.
  
  @param int $pid
  @return ProcessDetailsCollection