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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 _cache_get_last_in_slice(url_dict, start_int, total_int, authn_subj_list):
 """Return None if cache entry does not exist."""

    key_str = _gen_cache_key_for_slice(url_dict, start_int, total_int, authn_subj_list)
    # TODO: Django docs state that cache.get() should return None on unknown key.
    try:
        last_ts_tup = django.core.cache.cache.get(key_str)
    except KeyError:
        last_ts_tup = None
    logging.debug('Cache get. key="{}" -> last_ts_tup={}'.format(key_str, last_ts_tup))
    return last_ts_tup