computeDeep method
Implementation
void computeDeep(T node, [int initDeep = 0]) {
int d = initDeep;
List<T> nl = [node];
List<T> next = [];
while (nl.isNotEmpty) {
for (var c in nl) {
c._deep = d;
next.addAll(c.children);
}
d++;
nl = next;
next = [];
}
}