def _autobounds(self):
        """Simple calculation for bounds."""
        bounds = {}

        def check(prop, compare, extreme, val):
            opp = min if compare is max else max
            bounds.setdefault(prop, val)
            bounds[prop] = opp(compare(bounds[prop], val), extreme)

        def bound_check(lat_lon):
            lat, lon = lat_lon
            check('max_lat', max, 90, lat)
            check('min_lat', min, -90, lat)
            check('max_lon', max, 180, lon)
            check('min_lon', min, -180, lon)

        lat_lons = [lat_lon for feature in self._features.values() for
                    lat_lon in feature.lat_lons]
        if not lat_lons:
            lat_lons.append(self._default_lat_lon)
        for lat_lon in lat_lons:
            bound_check(lat_lon)

        return bounds
Simple calculation for bounds.