Why the node in the network needs control_deps

I don’t know why the node in the network needs control_deps. What is the intention for using control_deps.

I think it’s used for tracking the dependencies of the node. Are you trying to modify the graph?

I don’t know, what do your mean modify the graph? And why we need to tracking the dependencies? I just need to link two nodes which are related? Can you give me some examples that we do need the dependencies?