code: def jaccard(box_a, box_b):
      """Compute the jaccard overlap of two sets of boxes.  The jaccard overlap
      is simply the intersection over union of two boxes.  Here we operate on
      ground truth boxes and default boxes.
      E.g.:
          A ∩ B / A ∪ B = A ∩ B / (area(A) + area(B) - A ∩ B)
      Args:
          box_a: (tensor) Ground truth bounding boxes, Shape: [num_objects,4]
          box_b: (tensor) Prior boxes from priorbox layers, Shape: [num_priors,4]
      Return:
          jaccard overlap: (tensor) Shape: [box_a.size(0), box_b.size(0)]
      """
      inter = intersect(box_a, box_b)
      area_a = (
          ((box_a[:, 2] - box_a[:, 0]) * (box_a[:, 3] - box_a[:, 1]))
          .unsqueeze(1)
          .expand_as(inter)
      )  # [A,B]
      area_b = (
          ((box_b[:, 2] - box_b[:, 0]) * (box_b[:, 3] - box_b[:, 1]))
          .unsqueeze(0)
          .expand_as(inter)
      )  # [A,B]
      union = area_a + area_b - inter
      return inter / union
  
imports: import numpy
  import torch
  import torch.nn
  import torch.nn.functional
label_desc: Use image node_id 2 for calling a global function with example usage: jaccard(box_a, box_b) and returns: unknown