code: def update_cache(from_currency, to_currency):
  	
  	if check_update(from_currency, to_currency) is True:
  		ccache[from_currency][to_currency]['value'] = convert_using_api(from_currency, to_currency)
  		ccache[from_currency][to_currency]['last_update'] = time.time()
  		cache.write(ccache)
docs: update from_currency to_currency pair in cache if
  	last update for that pair is over 30 minutes ago by request API info