code: public function get($key, $fallback = true)
      {
          foreach ($this->getImages() as $image) {
              /* @var ImageInterface $image */
              if ($key == $image->getKey()) {
                  return $image;
              }
          }
  
          return !$fallback || self::ORIGINAL == $key ? null : $this->get(self::ORIGINAL);
      }
docs: Get an image
  
  If no image with the $key is found, the image with the key
  self::ORIGINAL is returned. Unless self::ORIGINAL is requested
  or $fallback is false - in that case NULL is returned.
  
  @param string $key
  @param bool   $fallback true: Return ORIGINAL image, if not found.
  
  @return ImageInterface|null