Adapter/FilesystemAssetAdapter.php
protected function getExtension(ContentfulAsset $asset, $locale)
    {
        $asset   = $this->assetRepo->findNewestById($asset->getSpaceId(), $asset->getId())->getOrCall(function () use ($asset) {
            throw new InvalidArgumentException(
                sprintf(
                    'Cannot find asset with id "%s" in space "%s"!',
                    $asset->getId(),
                    $asset->getSpaceId()
                )
            );
        });
        $guesser = ExtensionGuesser::getInstance();
        return $guesser->guess($asset->file[$locale]['contentType']);
    }
protected function getExtension(ContentfulAsset $asset, $locale)
    {
        $asset   = $this->assetRepo->findNewestById($asset->getSpaceId(), $asset->getId())->getOrCall(function () use ($asset) {
            throw new InvalidArgumentException(
                sprintf(
                    'Cannot find asset with id "%s" in space "%s"!',
                    $asset->getId(),
                    $asset->getSpaceId()
                )
            );
        });
        $guesser = ExtensionGuesser::getInstance();
        return $guesser->guess($asset->file[$locale]['contentType']);
    }
@param ContentfulAsset $asset
@param string          $locale

@return string|null
@throws InvalidArgumentException