Method push_back

src/ifcparse/IfcParse.cpp:1764–1774

    };

    void push_back(int level, IfcUtil::IfcBaseClass* instance) {
        if (mode_ == 0) {
            list_->push(instance);
        } else {
            auto& l = instances_by_level_[level];
            if (!l) {
                l.reset(new aggregate_of_instance);
            }
            l->push(instance);
        }
    }

    aggregate_of_instance::ptr get_list() const {
        if (mode_ == 0) {