clear method
void
clear()
Releases all nids and zeros every dense array. The onCapacityGrew callback is not fired; callers that maintain external per-nid arrays are responsible for clearing them too.
Implementation
void clear() {
_dataByNid.clear();
_childrenByNid.clear();
_parentByNid = Int32List(0);
_depthByNid = Int32List(0);
_expandedByNid = Uint8List(0);
_ancestorsExpandedByNid = Uint8List(0);
nids.clear();
}