code: private function fastlyRotate($angle)
      {
          $angle = (int) $angle;
  
          $orient = null;
          if ($angle == 90) {
              $orient = 'r';
          }
  
          if ($angle == -90 || $angle == 270) {
              $orient = 'l';
          }
  
          if ($angle == 180) {
              $orient = 3;
          }
  
          if ($orient !== null) {
              $this->fastlyParameters['orient'] = $orient;
          }
  
          return $this;
      }
docs: Fastly implementation of rotation
  
  @param int $angle
  @return \Magento\Catalog\Model\Product\Image