<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_from_cache(url):
 """ Retrieve a HTTP response json object from the cache. Parameters url : string the url of the request Returns ------- response_json : dict """

    # if the tool is configured to use the cache
    if settings.use_cache:
        # determine the filename by hashing the url
        filename = hashlib.md5(url.encode('utf-8')).hexdigest()

        cache_path_filename = os.path.join(settings.cache_folder, os.extsep.join([filename, 'json']))
        # open the cache file for this url hash if it already exists, otherwise
        # return None
        if os.path.isfile(cache_path_filename):
            with io.open(cache_path_filename, encoding='utf-8') as cache_file:
                response_json = json.load(cache_file)
            log('Retrieved response from cache file "{}" for URL "{}"'.format(cache_path_filename, url))
            return response_json