code: def load_hierarchical_lmdb_dataset(self, data_dir):
      lmdb_sets = {}
      dataset_idx = 0
      env = lmdb.open(
          data_dir,
          max_readers=32,
          readonly=True,
          lock=False,
          readahead=False,
          meminit=False,
      )
      txn = env.begin(write=False)
      num_samples = int(pickle.loads(txn.get(b"__len__")))
      lmdb_sets[dataset_idx] = {
          "dirpath": data_dir,
          "env": env,
          "txn": txn,
          "num_samples": num_samples,
      }
      return lmdb_sets
  
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 1 for calling the LMDBDataSetTableMaster obj's underlying member method code with example usage: obj.load_hierarchical_lmdb_dataset(data_dir) and returns: lmdb_sets