def METHOD_NAME(box1, box2, x1y1x2y2=False):
    """
    Returns the IoU of two bounding boxes
    """
    N, M = len(box1), len(box2)
    if x1y1x2y2:
        # Get the coordinates of bounding boxes
        b1_x1, b1_y1, b1_x2, b1_y2 = box1[:, 0], box1[:, 1], box1[:, 2], box1[:, 3]
        b2_x1, b2_y1, b2_x2, b2_y2 = box2[:, 0], box2[:, 1], box2[:, 2], box2[:, 3]
    else:
        # Transform from center and width to exact coordinates
        b1_x1, b1_x2 = box1[:, 0] - box1[:, 2] / 2, box1[:, 0] + box1[:, 2] / 2
        b1_y1, b1_y2 = box1[:, 1] - box1[:, 3] / 2, box1[:, 1] + box1[:, 3] / 2
        b2_x1, b2_x2 = box2[:, 0] - box2[:, 2] / 2, box2[:, 0] + box2[:, 2] / 2
        b2_y1, b2_y2 = box2[:, 1] - box2[:, 3] / 2, box2[:, 1] + box2[:, 3] / 2
    # get the coordinates of the intersection rectangle
    inter_rect_x1 = torch.max(b1_x1.unsqueeze(1), b2_x1)
    inter_rect_y1 = torch.max(b1_y1.unsqueeze(1), b2_y1)
    inter_rect_x2 = torch.min(b1_x2.unsqueeze(1), b2_x2)
    inter_rect_y2 = torch.min(b1_y2.unsqueeze(1), b2_y2)
    # Intersection area
    inter_area = torch.clamp(inter_rect_x2 - inter_rect_x1, 0) * torch.clamp(
        inter_rect_y2 - inter_rect_y1, 0
    )
    # Union Area
    b1_area = (b1_x2 - b1_x1) * (b1_y2 - b1_y1)
    b1_area = ((b1_x2 - b1_x1) * (b1_y2 - b1_y1)).view(-1, 1).expand(N, M)
    b2_area = ((b2_x2 - b2_x1) * (b2_y2 - b2_y1)).view(1, -1).expand(N, M)
    return inter_area / (b1_area + b2_area - inter_area + 1e-16)