code: public function getInstance()
      {
          if ($this->instance === null) {
              $this->instance = $this->jobFactory->create(
                  $this->klass,
                  $this->getPerformMethod()
              );
          }
  
          return $this->instance;
      }
docs: Get the instance of the class specified on this job.
  
  This instance will be used to call a perform method:
  - $payload['performMethod']
  - "perform" if not specified
  
  @return object
  
  @throws InvalidArgumentException