add method
Implementation
void add(String rebuildWhenPropertyChanged, BindingBase instanceToAdd) {
List<BindingBase> list =
_instancesToNotify[rebuildWhenPropertyChanged] ?? [];
if (!list.contains(instanceToAdd)) {
instanceToAdd.source.callback = propertyChanged;
list.add(instanceToAdd);
}
_instancesToNotify[rebuildWhenPropertyChanged] = list;
}