def METHOD_NAME(self, ymd):
    date_key = hmac_sha256(("AWS4" + self.password).encode(), ymd.encode())
    region_key = hmac_sha256(date_key, self.region.encode())
    service_key = hmac_sha256(region_key, b's3')
    signing_key = hmac_sha256(service_key, b'aws4_request')
    self.signing_key = (signing_key, ymd)