Usage: python get_imdb_keys.py "url" "out_file"

Output: a .json file in imdb_key_lists/<out_file>.json containing a list representation of all fetched keys.

Example: <python get_imdb_keys.py "https://www.imdb.com/chart/top?ref_=nv_mv_250" "top_250"> will generate a file top_250.json in ../imdb_key_lists/top_250.json.