code: @VisibleForTesting
  	public static boolean checkTickerFreshness(final Map<BitfinexStreamSymbol, Long> heartbeatValues) {
  		final long currentTime = System.currentTimeMillis();
  
  		final List<BitfinexStreamSymbol> outdatedSymbols = heartbeatValues.entrySet().stream()
  			.filter(e -> e.getValue() + TICKER_TIMEOUT < currentTime)
  			.map(Map.Entry::getKey)
  			.collect(Collectors.toList());
  
  		outdatedSymbols.forEach(symbol -> {
  			logger.debug("Symbol {} is outdated by {}ms",
  					symbol, currentTime - heartbeatValues.get(symbol));
  		});
  		return outdatedSymbols.isEmpty();
  	}
docs: Are all ticker up-to-date
  @return