why the code '''this->loss ...''' makes sense in layer.hpp?

[chenchr]

Hello. I've just read the source code of caffe. In layer.cpp, the function inline Dtype Layer<Dtype>::Forward(const vector<Blob<Dtype>*>& bottom,

    const vector<Blob<Dtype>*>& top), there are the code:

template <typename Dtype>
	inline Dtype Layer<Dtype>::Forward(const vector<Blob<Dtype>*>& bottom,
	const vector<Blob<Dtype>*>& top) {
	Dtype loss = 0;
	Reshape(bottom, top);
	switch (Caffe::mode()) {
	case Caffe::CPU:
	Forward_cpu(bottom, top);
	for (int top_id = 0; top_id < top.size(); ++top_id) {
	if (!this->loss(top_id)) { continue; }
	const int count = top[top_id]->count();
	const Dtype* data = top[top_id]->cpu_data();
	const Dtype* loss_weights = top[top_id]->cpu_diff();
	loss += caffe_cpu_dot(count, data, loss_weights);
	}
	break;
	case Caffe::GPU:
	Forward_gpu(bottom, top);
	#ifndef CPU_ONLY
	for (int top_id = 0; top_id < top.size(); ++top_id) {
	if (!this->loss(top_id)) { continue; }
	const int count = top[top_id]->count();
	const Dtype* data = top[top_id]->gpu_data();
	const Dtype* loss_weights = top[top_id]->gpu_diff();
	Dtype blob_loss = 0;
	caffe_gpu_dot(count, data, loss_weights, &blob_loss);
	loss += blob_loss;
	}
	#endif
	break;
	default:
	LOG(FATAL) << "Unknown caffe mode.";
	}
	return loss;
	}

I think the protected member of the class layer should be loss_, whose name ends with underline, however, in the code above, there is a line of code '''if (!this->loss(top_id)) { continue; }''', in the line 421 and 432 of the layer.cpp, where the member loss do not end with underline. I want to know where is the mistake I've made. Thanks!