A newbie question regarding torch tensor add

1

Perhaps a newbie question here, I checked the documentation here torch.add.

Question:

  1. what is the star “*” argument within the function as shown in the documentation?
    torch.add(input, other, *, alpha=1, out=None)

  2. from the documentation, what is the meaning of below lua statement?
    tt means timestep, gradInput[tt][1], input[tt][2], cumreward are all torch.Tensor()

      self.gradInput[tt][1]:add(
         input[tt][2]:squeeze(), -1, self.cumreward:select(2, shifted_tt))

Thank you in advance!!