Returns the WGS84 bbox of the specified tile

def tile_bbox(self, tile_indices):
        """
        Returns the WGS84 bbox of the specified tile
        """
        (z, x, y) = tile_indices
        topleft = (x * self.tilesize, (y + 1) * self.tilesize)
        bottomright = ((x + 1) * self.tilesize, y * self.tilesize)
        nw = self.unproject_pixels(topleft, z)
        se = self.unproject_pixels(bottomright, z)
        return nw + se