code: def dataset_traversal(self):
      lmdb_num = len(self.lmdb_sets)
      total_sample_num = 0
      for lno in range(lmdb_num):
          total_sample_num += self.lmdb_sets[lno]["num_samples"]
      data_idx_order_list = np.zeros((total_sample_num, 2))
      beg_idx = 0
      for lno in range(lmdb_num):
          tmp_sample_num = self.lmdb_sets[lno]["num_samples"]
          end_idx = beg_idx + tmp_sample_num
          data_idx_order_list[beg_idx:end_idx, 0] = lno
          data_idx_order_list[beg_idx:end_idx, 1] = list(
              range(tmp_sample_num)
          )
          data_idx_order_list[beg_idx:end_idx, 1] += 1
          beg_idx = beg_idx + tmp_sample_num
      return data_idx_order_list
  
imports: import numpy
  import os
  from paddle.io import Dataset
  import lmdb
  import cv2
  import string
  import six
  import pickle
  from PIL import Image
  from .imaug import transform, create_operators
label_desc: Use image node_id 3 for calling the LMDBDataSet obj's underlying member method code with example usage: obj.dataset_traversal() and returns: data_idx_order_list