def stats(self) -> pd.DataFrame:
        """Statistics about flights contained in the structure.
        Useful for a meaningful representation.
        """
        key = ["icao24", "callsign"] if self.flight_ids is None else "flight_id"
        return (
            self.data.groupby(key)[["timestamp"]]
            .count()
            .sort_values("timestamp", ascending=False)
            .rename(columns={"timestamp": "count"})
        )
Statistics about flights contained in the structure.
        Useful for a meaningful representation.