code: public function createWorkerPoolWithExpression($implementationExpression, $workerCount = null)
      {
          return WorkerPool::withExpression($this->bootstrapProfile, $implementationExpression, $workerCount);
      }
docs: @param string   $implementationExpression
  @param int|null $workerCount
  
  @throws Exception\InvalidArgumentException
  @throws Exception\RuntimeException
  
  @return WorkerPool