Where can I find guidance regarding caffe2's TensorProto object?

I want to ask at caffe2’s github “issues”, which now is apart of pytorch. It suggests me to ask my question here.

I’m reading caffe2’s tutorial codes, especially CIFAR-10: Part 1&2. It has some operations related to the object created by TensorProtos(), such as protos.add(), protos.extend(), reshape(). I suspect not all the operations belong to the TensorProtos object. But it seems I can’t find any references to those operations. What are their roles? What are they doing? How can I use them on my own?