Documentation on how to convert Signal to torch.Tensor (or smarter solution?)

[turian]

One gotcha is when we have a Signal but we want is just as a torch.Tensor, otherwise logging and pickling and lightning stuff fails. But I forget how to do that and it's undocumented.

Simplest fix is to document it.

Removing Signal might be a bad idea? Not sure. Possibly we convert it to namedtuple so I can be type-checked.

(p.s. should we start using typeguard? We can just drop it in and say every class should be typechecked at runtime)