code: public <T> boolean containsKey(StorageKey<T> key) {
      return storage.getItem(key.name()) != null;
    }
docs: Test if this storage contains a value for the specified key.
  
  <p>
  {@link StorageKeyFactory} is preferred to get a {@link StorageKey} instance for primitive types.
  </p>
  
  @param key the key whose presence in this storage is to be tested
  @param <T> the type of stored value
  @return <tt>true</tt> if this storage contains a value for the specified key.