code: def mean_std(self):
      if self._mean_std is None:
          with open(self.split_filename_mean_std, "r") as f:
              self._mean_std = json.load(f)
      return self._mean_std
  
imports: import numpy
  import os
  import json
  import h5py
  from tqdm import tqdm
  from torchmeta.utils.data import Dataset, ClassDataset, CombinationMetaDataset
  from torchmeta.datasets.utils import get_asset
label_desc: Use image node_id 6 for calling the PlantsShapeClassDataset obj's underlying member method code with example usage: obj.mean_std() and returns: self