def forward(self, output, mask, ind, target):
    pred = _transpose_and_gather_feat(output, ind)
    loss = self._reg_loss(pred, target, mask)
    return loss
def forward(self, output, mask, ind, target):
    pred = _transpose_and_gather_feat(output, ind)
    loss = self._reg_loss(pred, target, mask)
    return loss