src/Entity/ImageSet.php
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 : $this->get(self::ORIGINAL);
    }
public function get($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);
    }
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