How to use the traffic.core.Traffic.from_file function in traffic

def get_flight(filename: str, directory: Path) -> Union[Flight, Traffic]:
    flight: Union[None, Flight, Traffic] = Traffic.from_file(
        directory / f"{filename}.json.gz", dtype={"icao24": str}
    )
    if flight is None:
        raise RuntimeError(f"File {filename}.json.gz not found in {directory}")
    icao24 = set(flight.data.icao24)
    if len(icao24) == 1:
        # easier way to cast...
        flight = Flight(flight.data)
    # -- Dealing with time-like features --
    if "hour" in flight.data.columns:
        flight = flight.assign(
            hour=lambda df: pd.to_datetime(df.hour * 1e9).dt.tz_localize("utc")
        )
    if "last_position" in flight.data.columns:
        flight = flight.assign(
            last_position=lambda df: pd.to_datetime(

options = {
            "caption": "Open file",
            "filter": (
                "Pandas DataFrame (*.pkl);;"
                "CSV files (*.csv);;"
                "Sqlite3 files (*.db)"
            ),
            #             "filter": "Data files (*.csv *.pkl)",
            "directory": os.path.expanduser("~"),
        }

        self.filename = QFileDialog.getOpenFileName(self, **options)[0]
        if self.filename == "":
            return
        self.filename = Path(self.filename)
        self._traffic = Traffic.from_file(self.filename)

        assert self._traffic is not None
        self._tview = self._traffic.sort_values("timestamp")
        assert self._tview is not None
        self.open_dropdown.setItemText(0, self.filename.name)
        self.map_plot.default_plot(self._tview)

        self.identifier_select.clear()
        for callsign in sorted(cast(Set[str], self._tview.callsigns)):
            self.identifier_select.addItem(callsign)

        self.set_time_range()
        self.set_float_columns()

)
    squawk7700 = Traffic.from_file(filename)
    assert squawk7700 is not None
    squawk7700 = squawk7700.merge(
        metadata.drop(columns=["callsign", "icao24"]), on="flight_id"
    )
    squawk7700.metadata = metadata  # type: ignore
    return squawk7700


datasets = dict(
    paris_toulouse_2017=dict(
        url="https://ndownloader.figshare.com/files/20291055",
        md5sum="e869a60107fdb9f092f5abbb3b43a2c0",
        filename="city_pair_dataset.parquet",
        reader=Traffic.from_file,
    ),
    airspace_bordeaux_2017=dict(
        url="https://ndownloader.figshare.com/files/20291040",
        md5sum="f7b057f12cc735a15b93984b9ae7b8fc",
        filename="airspace_dataset.parquet",
        reader=Traffic.from_file,
    ),
    landing_zurich_2019=dict(
        url="https://ndownloader.figshare.com/files/20291079",
        md5sum="c5577f450424fa74ca673ed8a168c67f",
        filename="landing_dataset.parquet",
        reader=Traffic.from_file,
    ),
    squawk7700=dict(
        url=f"{_squawk7700_url}/files/squawk7700_trajectories.parquet.gz",
        md5sum="8ed5375d92bd7b7b94ea03c0533d959e",

group = parser.add_mutually_exclusive_group()
    group.add_argument(
        "--head",
        dest="head",
        action="store_true",
        help="print the first lines of the traffic file",
    )
    parser.add_argument(
        "callsigns",
        nargs=argparse.REMAINDER,
        help="display specific information about specific flights",
    )

    args = parser.parse_args(args)
    t = Traffic.from_file(args.filename)
    assert t is not None

    print("Traffic with {} identifiers".format(len(t)))
    print(t)
    print()
    print("with the following features:")
    print(t.data.columns)

    if args.head:
        print()
        print("Head of the DataFrame:")
        print(t.data.head())

    if args.callsigns:
        for callsign in args.callsigns:
            print()

def _squawk7700_reader(filename):
    metadata = get_dataset(
        dict(
            url=f"{_squawk7700_url}/files/squawk7700_metadata.csv",
            md5sum="4d33ff84a05742136f3733692bf944e6",
            filename="squawk7700_metadata.csv",
            reader=pd.read_csv,
        )
    )
    squawk7700 = Traffic.from_file(filename)
    assert squawk7700 is not None
    squawk7700 = squawk7700.merge(
        metadata.drop(columns=["callsign", "icao24"]), on="flight_id"
    )
    squawk7700.metadata = metadata  # type: ignore
    return squawk7700