code: @SuppressWarnings("unchecked")
  	public <T> Map<Serializable, T> get(Collection<? extends Serializable> keys) {
  		Map<Serializable, T> result = Maps.newHashMapWithExpectedSize(keys.size());
  		for (Serializable key : keys) {
  			T value = (T) contents.getIfPresent(key);
  			if (value != null) {
  				result.put(key, value);
  			}
  		}
  		if (log.isDebugEnabled() && !result.isEmpty()) {
  			log.debug("Level 1 cache multiple hit: {}", result.keySet());
  		}
  		return result;
  	}
docs: Return the list of values from cache. Only entries with non-null value will be returned