def filter_tiles(tiles_fname, out_fname, bbox):
# parse the bounding box arguments
bbox = BoundingBox.fromStr(bbox)
# load all tiles from the tile-spec json file that are relevant to our bounding box
relevant_tiles = load_tiles(tiles_fname, bbox)
# Create a tile-spec file that includes all relevant tiles
with open(out_fname, 'w') as outfile:
json.dump(relevant_tiles, outfile, sort_keys=True, indent=4)
