hasEdgeTo method
Determine if there is such a valued directed link
(Optional) Only if it matches any of anyTags
and matches all items in allTags
Implementation
bool hasEdgeTo(from, to, key,
{List anyTags = const [], List allTags = const []}) {
final _f = _map_add_or_get(from, _newNode);
final _t = _map_add_or_get(to, _newNode);
return _check_hasToVal_and_all_any_val_tags(_f, _t, key,
anyTags: anyTags, allTags: allTags);
}