class_docstr: Base class for a meta-dataset.
  
  Parameters
  ----------
  meta_train : bool (default: `False`)
      Use the meta-train split of the dataset. If set to `True`, then the
      arguments `meta_val` and `meta_test` must be set to `False`. Exactly one 
      of these three arguments must be set to `True`.
  
  meta_val : bool (default: `False`)
      Use the meta-validation split of the dataset. If set to `True`, then the 
      arguments `meta_train` and `meta_test` must be set to `False`. Exactly one 
      of these three arguments must be set to `True`.
  
  meta_test : bool (default: `False`)
      Use the meta-test split of the dataset. If set to `True`, then the 
      arguments `meta_train` and `meta_val` must be set to `False`. Exactly one 
      of these three arguments must be set to `True`.
  
  meta_split : string in {'train', 'val', 'test'}, optional
      Name of the split to use. This overrides the arguments `meta_train`, 
      `meta_val` and `meta_test`.
  
  target_transform : callable, optional
      A function/transform that takes a target, and returns a transformed 
      version. See also `torchvision.transforms`.
  
  dataset_transform : callable, optional
      A function/transform that takes a dataset (ie. a task), and returns a 
      transformed version of it. E.g. `transforms.ClassSplitter()`.
code: def meta_split(self):
      if self._meta_split is None:
          if self.meta_train:
              self._meta_split = "train"
          elif self.meta_val:
              self._meta_split = "val"
          elif self.meta_test:
              self._meta_split = "test"
          else:
              raise NotImplementedError()
      return self._meta_split
  
imports: import sys
  import numpy
  import warnings
  from copy import deepcopy
  from itertools import combinations
  from ordered_set import OrderedSet
  from torchvision.transforms import Compose
  from torchmeta.utils.data.task import ConcatTask
  from torchmeta.transforms import FixedCategory, Categorical, DefaultTargetTransform
  from torchmeta.transforms.utils import wrap_transform
label_desc: Use image node_id 2 for calling the MetaDataset obj's underlying member method code with example usage: obj.meta_split() and returns: self