interface WeakValueReference<K, V, E extends InternalEntry<K, V, E>> {
    /**
     * Returns the current value being referenced, or {@code null} if there is none (e.g. because
     * either it got collected, or {@link #clear} was called, or it wasn't set in the first place).
     */
    @Nullable V get();

    /** Returns the entry which contains this {@link WeakValueReference}. */
    E getEntry();

  interface WeakValueReference<K, V, E extends InternalEntry<K, V, E>> {
    /**
     * Returns the current value being referenced, or {@code null} if there is none (e.g. because
     * either it got collected, or {@link #clear} was called, or it wasn't set in the first place).
     */
    @Nullable V get();

    /** Returns the entry which contains this {@link WeakValueReference}. */
    E getEntry();