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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def export_image(self, bbox, zoomlevel, imagepath):
 """ Writes to ``imagepath`` the tiles for the specified bounding box and zoomlevel. """

        assert has_pil, _("Cannot export image without python PIL")
        grid = self.grid_tiles(bbox, zoomlevel)
        width = len(grid[0])
        height = len(grid)
        widthpix = width * self.tile_size
        heightpix = height * self.tile_size

        result = Image.new("RGBA", (widthpix, heightpix))
        offset = (0, 0)
        for i, row in enumerate(grid):
            for j, (x, y) in enumerate(row):
                offset = (j * self.tile_size, i * self.tile_size)
                img = self._tile_image(self.tile((zoomlevel, x, y)))
                result.paste(img, offset)
        logger.info(_("Save resulting image to '%s'") % imagepath)
        result.save(imagepath)