mapSubscriptions method
Registers subscriptions associated with node for later cancellation.
See cancelSubscriptions.
Implementation
void mapSubscriptions(T node, List<Object> subscriptions) {
if (subscriptions.isEmpty) return;
final elementsSubscriptions = _elementsSubscriptions ??=
WeakKeyMap(autoPurge: false, onPurgedValues: _onPurgedSubscriptions);
var l = elementsSubscriptions[node] ??= [];
l.addAll(subscriptions);
}