*
     * @param key the key
     * @param value the value
     */
    void put(K key, V value);

    /**
     * Adds a map entry to the property value.
     *
     * <p>The given provider will be queried when the value of this property is queried.
     * This property will have no value when the given provider has no value.
     *
     * @param key the key