[C4_W4_Assignment] what does trax.data.AddLossWeights do?

what does trax.data.AddLossWeights do?

From the docs and code repository:

  - If the stream consists of pairs `(inputs, targets)`, a loss mask is added
    that is creates as a tensor of ones of the same shape as targets.
  - If `id_to_mask` is not `None`, and the stream (after the previous point)
    has triples `(inputs, targets, weights)`, the weights are multiplied by a
    0/1 mask that is 0 iff targets is equal to `id_to_mask` (1 otherwise).

In simple words - model does not try to learn padding (id_to_mask).