code: public function addInstance($process_id, $instance_create_item)
      {
          list($response) = $this->addInstanceWithHttpInfo($process_id, $instance_create_item);
          return $response;
      }
docs: Operation addInstance
  
  
  
  @param string $process_id Process ID related to the instance (required)
  @param \ProcessMaker\PMIO\Model\InstanceCreateItem $instance_create_item JSON API response with the instance object to add (required)
  @return \ProcessMaker\PMIO\Model\InstanceItem
  @throws \ProcessMaker\PMIO\ApiException on non-2xx response