private boolean checkExtension(String ext) {
        return IMAGE_SUBTYPES_ALLOWED.matcher(ext).matches();
    }
{@inheritDoc}

<p>Serves the blob as a stream

@param uid file's unique ID.
@return the file in response.
manager/api/rest-impl/src/main/java/io/apiman/manager/api/rest/impl/BlobResourceImpl.java