default boolean contains(@NonNull CloudKeyHolder<?> keyHolder) {
        return this.contains(keyHolder.key());
    }
Returns whether the registry contains a value associated with the given {@code keyHolder}.

@param keyHolder the holder of the key
@return {@code true} if the value exists, or {@code false} if it does not
cloud-core/src/main/java/org/incendo/cloud/key/CloudKeyContainer.java