Returns: Nx4

def decoded_output_boxes_class_agnostic(self):
        """ Returns: Nx4 """
        assert self._bbox_class_agnostic
        box_logits = tf.reshape(self.box_logits, [-1, 4])
        decoded = decode_bbox_target(
            box_logits / self.bbox_regression_weights,
            self.proposals.boxes
        )
        return decoded