<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _manual_overrides(_cache_date=None):
 """Read the overrides file. An attempt is made to read the file as it currently stands on GitHub, and then only if that fails is the included file used. """

    log = logging.getLogger('ciu')
    request = requests.get("https://raw.githubusercontent.com/brettcannon/"
                           "caniusepython3/master/caniusepython3/overrides.json")
    if request.status_code == 200:
        log.info("Overrides loaded from GitHub and cached")
        overrides = request.json()
    else:
        log.info("Overrides loaded from included package data and cached")
        raw_bytes = pkgutil.get_data(__name__, 'overrides.json')
        overrides = json.loads(raw_bytes.decode('utf-8'))
    return frozenset(map(packaging.utils.canonicalize_name, overrides.keys()))