def get_offer_ids(soup):
    """
    get offers ids from a html page

    Parameters
    ----------
    soup : BeautifulSoup
        html code

    Returns
    -------
    list[string]:
        offers ids
    """
    l_offer_ids = []

    # find all <a> tags from html code and get id if it starts with "job"
    a_tags = soup.find_all("a")
    for a in a_tags:
        try:
            if a["id"].startswith("job_"):
                l_offer_ids.append(a["id"])
        except KeyError:
            pass

    return l_offer_ids