Encode a set of proposals with respect to some
        reference boxes

        Arguments:
            reference_boxes (Tensor): reference boxes
            proposals (Tensor): boxes to be encoded

def encode(self, reference_boxes, proposals):
        """
        Encode a set of proposals with respect to some
        reference boxes

        Arguments:
            reference_boxes (Tensor): reference boxes
            proposals (Tensor): boxes to be encoded
        """

        TO_REMOVE = 1  # TODO remove
        ex_widths = proposals[:, 2] - proposals[:, 0] + TO_REMOVE
        ex_heights = proposals[:, 3] - proposals[:, 1] + TO_REMOVE
        ex_ctr_x = proposals[:, 0] + 0.5 * ex_widths
        ex_ctr_y = proposals[:, 1] + 0.5 * ex_heights

        gt_widths = reference_boxes[:, 2] - reference_boxes[:, 0] + TO_REMOVE
        gt_heights = reference_boxes[:, 3] - reference_boxes[:, 1] + TO_REMOVE
        gt_ctr_x = reference_boxes[:, 0] + 0.5 * gt_widths
        gt_ctr_y = reference_boxes[:, 1] + 0.5 * gt_heights

        wx, wy, ww, wh = self.weights
        targets_dx = wx * (gt_ctr_x - ex_ctr_x) / ex_widths
        targets_dy = wy * (gt_ctr_y - ex_ctr_y) / ex_heights
        targets_dw = ww * torch.log(gt_widths / ex_widths)
        targets_dh = wh * torch.log(gt_heights / ex_heights)

        targets = torch.stack((targets_dx, targets_dy, targets_dw, targets_dh), dim=1)
        return targets