    def forward(self, input, target):
        """
        Args:
            input: (b x t x d)
            target: (b x t)
        Returns:
            2 lists: output for each cutoff section and new targets by cut off
        """

        input = input.contiguous().view(-1, input.size(-1))
        input = self.dropout_module(input)

        new_target, target_idxs = self.adapt_target(target)
        output = [self.head(input)]

        for i in range(len(target_idxs)):
            if target_idxs[i] is not None:
                output.append(self.tail[i](input.index_select(0, target_idxs[i])))
            else:
                output.append(None)

        return output, new_target
Args:
input: (b x t x d)
target: (b x t)
Returns:
2 lists: output for each cutoff section and new targets by cut off
fairseq/modules/adaptive_softmax.py