def METHOD_NAME(self):
    ds = DataSource(str(ZIPCODE_SHAPEFILE))
    layer = ds[0]
    zipcodes: Dict[str, Any] = {}
    for feature in layer:
        zipcode = str(feature["ZIPCODE"])
        geom = feature.geom
        geom.transform(4326)
        if zipcode in zipcodes:
            zipcodes[zipcode] = zipcodes[zipcode].union(geom.geos)
        else:
            zipcodes[zipcode] = geom.geos
    for zipcode, geos_geom in zipcodes.items():
        print(f"Saving zipcode {zipcode}.")
        instance = get_or_construct(Zipcode, zipcode=zipcode)
        instance.geom = to_multipolygon(geos_geom)
        instance.save()
    print(f"Loaded {len(zipcodes)} zipcodes across {len(layer)} features.")