def __init__(self, proposals, box_logits, label_logits, gt_boxes, bbox_regression_weights):
        """
        Args:
            proposals: BoxProposals
            box_logits: Nx#classx4 or Nx1x4, the output of the head
            label_logits: Nx#class, the output of the head
            gt_boxes: Mx4
            bbox_regression_weights: a 4 element tensor
        """
        for k, v in locals().items():
            if k != 'self' and v is not None:
                setattr(self, k, v)
        self._bbox_class_agnostic = int(box_logits.shape[1]) == 1
        self._num_classes = box_logits.shape[1]

        Args:
            proposals: BoxProposals
            box_logits: Nx#classx4 or Nx1x4, the output of the head
            label_logits: Nx#class, the output of the head
            gt_boxes: Mx4
            bbox_regression_weights: a 4 element tensor
        
examples/FasterRCNN/modeling/model_frcnn.py