def METHOD_NAME(self, **kwargs):
    """/OPTIONS handler for preflight CORS checks.
    When a browser is making a CORS request, it may sometimes first
    send an OPTIONS request, to check whether the server understands the
    CORS protocol. This is optional, and doesn't happen for every request
    or in every browser. If an OPTIONS request does get sent, and is not
    then handled by the server, the browser will fail the underlying
    request.
    The proper way to handle this is to send a 204 response ("no content")
    with the CORS headers attached. (These headers are automatically added
    to every outgoing response, including OPTIONS responses,
    via set_default_headers().)
    See https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request
    """
    self.set_status(204)
    self.finish()