code: def pbf(self, bbox, geo_col=None, scale=4096):
          
          col = geo_col or self.geo_field.name
          w, s, e, n = bbox.extent
          trans = self._trans_scale(col, -w, -s,
                                    scale / (e - w),
                                    scale / (n - s))
          g = AsText(trans)
          return self.annotate(pbf=g)
docs: Returns tranlated and scaled geometries suitable for Mapbox vector
          tiles.