I am a newbie to lua / torch. I notice that the variable \_ is used a lot, especially in iterators. Example:

```
for _, node in ipairs(protos.rnn.forwardnodes) do
    a, b = whatever(a,b)
end

```

this 'variable naming convention' (so to speak) is used in other circumstances as well, as in:

```
local _,loss = optimizer(feval,params, optim_state)

```

Does \_ have any special meaning or is it just one more variable name, among the many possible names?