code: def tileslist(self, bbox, zoomlevels):
          
          proj = GoogleProjection(self.tile_size, zoomlevels, self.tile_scheme)
          return proj.tileslist(bbox)
docs: Build the tiles list within the bottom-left/top-right bounding
          box (minx, miny, maxx, maxy) at the specified zoom levels.
          Return a list of tuples (z,x,y)