code: def iou(boxes1, boxes2):
    
    intersect = intersection(boxes1, boxes2)
    area1 = area(boxes1)
    area2 = area(boxes2)
    union = np.expand_dims(area1, axis=1) + np.expand_dims(
        area2, axis=0) - intersect
    return intersect / union
docs: Computes pairwise intersection-over-union between box collections.
  
    Args:
      boxes1: a numpy array with shape [N, 4] holding N boxes.
      boxes2: a numpy array with shape [M, 4] holding M boxes.
  
    Returns:
      a numpy array with shape [N, M] representing pairwise iou scores.