Is grad_fn for a non-differentiable function that function's inverse?

What is grad_fn for a non-differentiable function like grad_fn=<SliceBackward0>, grad_fn=<ViewBackward0>, etc.? Is it simply the function’s inverse operation?

Where in the source code can I see the implementation of SliceBackward0, ViewBackward0, etc.? I assume it’s in their backward() static methods somewhere.