class_docstr: Open Images Challenge dataset for detection.
  
  Args:
      ann_file (str): Open Images Challenge box annotation in txt format.
docstr: Get the matrix of class hierarchy from the hierarchy file.
  
  Args:
      hierarchy_file (str): File path to the hierarchy for classes.
  
  Returns:
      np.ndarray: The matrix of the corresponding
      relationship between the parent class and the child class,
      of shape (class_num, class_num).
docstr_tok: ["Get","the","matrix","of","class","hierarchy","from","the","hierarchy","file",".","Args",":","hierarchy_file","(","str",")",":","File","path","to","the","hierarchy","for","classes",".","Returns",":","np.ndarray",":","The","matrix","of","the","corresponding","relationship","between","the","parent","class","and","the","child","class",",","of","shape","(","class_num",",","class_num",")","."]
code: def _get_relation_matrix(self, hierarchy_file: str) -> np.ndarray:
      """Get the matrix of class hierarchy from the hierarchy file.
  
      Args:
          hierarchy_file (str): File path to the hierarchy for classes.
  
      Returns:
          np.ndarray: The matrix of the corresponding
          relationship between the parent class and the child class,
          of shape (class_num, class_num).
      """
      with get_local_path(
          hierarchy_file, backend_args=self.backend_args
      ) as local_path:
          class_label_tree = np.load(local_path, allow_pickle=True)
      return class_label_tree[1:, 1:]
  
imports: import csv
  import os.path
  from collections import defaultdict
  from typing import Dict, List, Optional
  import numpy
  from mmengine.fileio import get_local_path, load
  from mmengine.utils import is_abs
  from mmdet.registry import DATASETS
  from .base_det_dataset import BaseDetDataset
label_desc: Use image node_id 5 for calling the OpenImagesChallengeDataset obj's underlying member method code with example usage: obj._get_relation_matrix(hierarchy_file) and returns: class_label_tree