code: private function disableFastly()
      {
          $this->configWriter->save(
              'system/full_page_cache/caching_application',
              \Magento\PageCache\Model\Config::BUILT_IN
          );
          $this->output->writeln(
              '<info>Fastly Caching Application Deactivated, default built in Caching mechanism set.</info>',
              OutputInterface::OUTPUT_NORMAL
          );
      }
docs: Disable Fastly