Clarification for the forward function of the SequenceSummary class from modeling_utils.py

Hello,
I have a question about the documentation strings provided for the forward function of the SequenceSummary class from modeling_utils.py:

So when cls_index is not specified as the argument in SequenceSummary() statement, is the last token of the sequence used for the classification task? The entire sentence for the description is somewhat awkward…

Thanks,