code: def zoom_bbox(self, bbox):
          
          try:
              bbox.transform(self.map.srs)
          except gdal.GDALException:
              pass
          else:
              self.map.zoom_to_box(mapnik.Box2d(*bbox.extent))
docs: Zoom map to geometry extent.
  
          Arguments:
          bbox -- OGRGeometry polygon to zoom map extent