hasEdge method
Determine if there is a value link between 2 nodes
(Optional) Only if it matches any of anyTags
and matches all items in allTags
Implementation
bool hasEdge(a, b, key, {List anyTags = const [], List allTags = const []}) {
return _Tuple2(a, b)
.map((v) => _map_add_or_get(v, _newNode))
.mutual((f, t) => _check_hasToVal_and_all_any_val_tags(f, t, key,
anyTags: anyTags, allTags: allTags))
.toDo(_or);
}