code: def __call__(self, order="ltrb"):
      # 根据需求返回对应格式的default box
      if order == "ltrb":
          return self.dboxes_ltrb
  
      if order == "xywh":
          return self.dboxes
  
imports: from math import sqrt
  import itertools
  import torch
  import torch.nn.functional
  from torch.jit.annotations import Tuple, List
  from torch import nn, Tensor
  import numpy
label_desc: Use image node_id 4 for calling the DefaultBoxes obj's underlying member method code with example usage: obj.__call__(order) and returns: self, self