22 return _back_pointers.size();
31 if (model_index >= 0 && model_index < (
int)_back_pointers.size()) {
32 return _back_pointers[model_index] !=
nullptr;
43 if (model_index >= 0 && model_index < (
int)_back_pointers.size()) {
44 return _back_pointers[model_index];