Zoom map to geometry extent.

        Arguments:
        bbox -- OGRGeometry polygon to zoom map extent

def zoom_bbox(self, bbox):
        """Zoom map to geometry extent.

        Arguments:
        bbox -- OGRGeometry polygon to zoom map extent
        """
        try:
            bbox.transform(self.map.srs)
        except gdal.GDALException:
            pass
        else:
            self.map.zoom_to_box(mapnik.Box2d(*bbox.extent))