`neg_iou_thresh_lo` value in `ProposalTargetCreator`

[Tsukasa Takagi]

Hi,

I want to know that the value 0.0 of neg_iou_thresh_lo is intended or not.
In the Fast R-CNN paper, it seems that the assignment for negative samples is decided when between the sample and GT IoU is ranged in [0.1, 0.5). (in section Mini-batch sampling).

https://arxiv.org/pdf/1504.08083.pdf

https://github.com/chainer/chainercv/blob/master/chainercv/links/model/faster_rcnn/utils/proposal_target_creator.py#L36