code: @SuppressWarnings("unchecked")
      public static <T extends Config> T get(Object key) {
          return (T) CACHE.get(key);
      }
docs: Gets from the cache the {@link Config} instance identified by the given key.
  
  @param key       the key object to be used to identify the instance in the cache.
  @param <T>       type of the interface.
  @return          the {@link Config} object from the cache if exists, or <code>null</code> if it doesn't.