pub fn store_signal_value_opt_mixin<A, TValue, TSignal>(
    source_signal: TSignal,
    target_mutable: &Mutable<TValue>
) -> impl FnOnce(DomBuilder<A>) -> DomBuilder<A>where
    A: AsRef<Element>,
    TValue: 'static,
    TSignal: Signal<Item = Option<TValue>> + 'static,