def METHOD_NAME(self, url=None):
    """
    Download kernel source.
    :param url: override the url from where to fetch the kernel
                source tarball
    :type url: str or None
    """
    full_url = self._build_kernel_url(base_url=url)
    self.asset_path = asset.Asset(
        full_url,
        asset_hash=None,
        algorithm=None,
        locations=None,
        cache_dirs=self.data_dirs,
    ).fetch()