def save_neighbour_info(self, cache_dir, mask=None, **kwargs):
        """Cache resampler's index arrays if there is a cache dir."""
        if cache_dir:
            mask_name = getattr(mask, 'name', None)
            filename = self._create_cache_filename(
                cache_dir, mask=mask_name, **kwargs)
            LOG.info('Saving kd_tree neighbour info to %s', filename)
            cache = self._read_resampler_attrs()
            # update the cache in place with persisted dask arrays
            self._apply_cached_indexes(cache, persist=True)
            self._index_caches[mask_name] = cache
            np.savez(filename, **cache)
Cache resampler's index arrays if there is a cache dir.