code: public function log($message, ...$args)
      {
          if ($this->logger) {
              $args[] = $this->stopwatch ? microtime(true) - $this->stopwatch : 0;
              $this->logger->debug(sprintf($message . ' (%.2fs)', ...$args));
          }
          return $this;
      }
docs: Log a debug message, and append time elapsed since ->run() was called
  
  @param string $message sprintf compatible string
  @param mixed[] $args Data to pass to sprintf
  @return self