code: public V first(K key) {
  		key = sanitizeKey(key);
  		List<V> values = map.get(key);
  
  		/*
  		 * The list can be null, but never empty. Empty lists are removed from
  		 * the map.
  		 */
  		return (values == null) ? null : values.get(0);
  	}
docs: Gets the first value that's associated with a key.
  @param key the key
  @return the first value or null if the key doesn't exist