def get_reference_id(url: str):
    """
    Return the reference id from a URL
    For example:
    >>> get_reference_id("https://github.com/advisories/GHSA-c9hw-wf7x-jp9j")
    'GHSA-c9hw-wf7x-jp9j'
    """
    _url, _, ref_id = url.strip("/").rpartition("/")
    return ref_id