code: public function getTempDirectory()
      {
          if (is_null($this->tempDirectory)) {
              $root = sys_get_temp_dir();
              if (!is_dir($root . '/humbug')) {
                  mkdir($root . '/humbug', 0777, true);
              }
              $this->tempDirectory = $root . '/humbug';
          }
          return $this->tempDirectory;
      }
docs: Get the cache directory of the project being mutated
  
  @return string