def METHOD_NAME(self, session=None, chamber=None):
    chambers = [chamber] if chamber else ["upper", "lower"]
    votes_url = VOTES_URLS.get(session)
    if not votes_url:
        self.warning("no house votes URL for %s", session)
        return
    html = self.get(votes_url).text
    doc = lxml.html.fromstring(html)
    for chamber in chambers:
        prefix = {"lower": "H", "upper": "S"}[chamber]
        xpath = '//a[contains(@href, "votesbynumber.asp?billnum=%s")]' % prefix
        links = doc.xpath(xpath)
        for link in links:
            bill_id = link.text
            link_url = link.get("href")
            yield from self.scrape_votes(chamber, session, bill_id, link_url)