How to use the gpxpy.utils.is_numeric function in gpxpy

Maximum longitude of track in decimal degrees [-180, 180]
        """
        min_lat = None
        max_lat = None
        min_lon = None
        max_lon = None
        for track in self.tracks:
            bounds = track.get_bounds()

            if not mod_utils.is_numeric(min_lat) or bounds.min_latitude < min_lat:
                min_lat = bounds.min_latitude
            if not mod_utils.is_numeric(max_lat) or bounds.max_latitude > max_lat:
                max_lat = bounds.max_latitude
            if not mod_utils.is_numeric(min_lon) or bounds.min_longitude < min_lon:
                min_lon = bounds.min_longitude
            if not mod_utils.is_numeric(max_lon) or bounds.max_longitude > max_lon:
                max_lon = bounds.max_longitude

        return GPXBounds(min_lat, max_lat, min_lon, max_lon)

Maximum latitude of track in decimal degrees [-90, 90]
            min_longitude : float
                Minimum longitude of track in decimal degrees [-180, 180]
            max_longitude : float
                Maximum longitude of track in decimal degrees [-180, 180]
        """
        min_lat = None
        max_lat = None
        min_lon = None
        max_lon = None
        for track in self.tracks:
            bounds = track.get_bounds()

            if not mod_utils.is_numeric(min_lat) or bounds.min_latitude < min_lat:
                min_lat = bounds.min_latitude
            if not mod_utils.is_numeric(max_lat) or bounds.max_latitude > max_lat:
                max_lat = bounds.max_latitude
            if not mod_utils.is_numeric(min_lon) or bounds.min_longitude < min_lon:
                min_lon = bounds.min_longitude
            if not mod_utils.is_numeric(max_lon) or bounds.max_longitude > max_lon:
                max_lon = bounds.max_longitude

        return GPXBounds(min_lat, max_lat, min_lon, max_lon)

Minimum longitude of track in decimal degrees [-180, 180]
            max_longitude : float
                Maximum longitude of track in decimal degrees [-180, 180]
        """
        min_lat = None
        max_lat = None
        min_lon = None
        max_lon = None
        for track in self.tracks:
            bounds = track.get_bounds()

            if not mod_utils.is_numeric(min_lat) or bounds.min_latitude < min_lat:
                min_lat = bounds.min_latitude
            if not mod_utils.is_numeric(max_lat) or bounds.max_latitude > max_lat:
                max_lat = bounds.max_latitude
            if not mod_utils.is_numeric(min_lon) or bounds.min_longitude < min_lon:
                min_lon = bounds.min_longitude
            if not mod_utils.is_numeric(max_lon) or bounds.max_longitude > max_lon:
                max_lon = bounds.max_longitude

        return GPXBounds(min_lat, max_lat, min_lon, max_lon)

Minimum latitude of track in decimal degrees [-90, 90]
            max_latitude : float
                Maximum latitude of track in decimal degrees [-90, 90]
            min_longitude : float
                Minimum longitude of track in decimal degrees [-180, 180]
            max_longitude : float
                Maximum longitude of track in decimal degrees [-180, 180]
        """
        min_lat = None
        max_lat = None
        min_lon = None
        max_lon = None
        for track in self.tracks:
            bounds = track.get_bounds()

            if not mod_utils.is_numeric(min_lat) or bounds.min_latitude < min_lat:
                min_lat = bounds.min_latitude
            if not mod_utils.is_numeric(max_lat) or bounds.max_latitude > max_lat:
                max_lat = bounds.max_latitude
            if not mod_utils.is_numeric(min_lon) or bounds.min_longitude < min_lon:
                min_lon = bounds.min_longitude
            if not mod_utils.is_numeric(max_lon) or bounds.max_longitude > max_lon:
                max_lon = bounds.max_longitude

        return GPXBounds(min_lat, max_lat, min_lon, max_lon)