def METHOD_NAME(cross_walk):
    """
    From a given crosswalk csv path, generate a dict mapping old_full_code to
    a list of the new codes originating from that source.
    """
    links = defaultdict(list)
    cross_walk = pd.read_csv(cross_walk, delimiter="|", encoding="unicode_escape", dtype=str)
    for _, r in cross_walk.iterrows():
        old_full_code = f"{r['SRS_SUBJ_CODE']}-{r['SRS_COURSE_NUMBER']}"
        new_full_code = f"{r['NGSS_SUBJECT']}-{r['NGSS_COURSE_NUMBER']}"
        links[old_full_code].append(new_full_code)
    return links