code: public function deleteInstance($process_id, $instance_id)
      {
          list($response) = $this->deleteInstanceWithHttpInfo($process_id, $instance_id);
          return $response;
      }
docs: Operation deleteInstance
  
  
  
  @param string $process_id Process ID (required)
  @param string $instance_id ID of the instance to delete (required)
  @return \ProcessMaker\PMIO\Model\ResultSuccess
  @throws \ProcessMaker\PMIO\ApiException on non-2xx response