class_docstr: Base class for MNIST, cifar10, etc.
code: def __mx_handle__(self):
      if self.handle is None:
          from ._internal import NDArrayDataset, GroupDataset
  
          self.handle = GroupDataset(
              datasets=(
                  NDArrayDataset(arr=default_array(self._data)),
                  NDArrayDataset(arr=default_array(self._label)),
              )
          )
      return self.handle
  
imports: import os
  from ...None import recordio, ndarray
  from ...util import default_array
label_desc: Use image node_id 5 for calling the _DownloadedDataset obj's underlying member method code with example usage: obj.__mx_handle__() and returns: self