code: def test_not_implemented_ds(self):
      class DS0(elegy.data.Dataset):
          ...
  
      class DS1(elegy.data.Dataset):
          def __len__(self):
              return 5
  
      for DS in [DS0, DS1]:
          ds = DS()
          loader = elegy.data.DataLoader(ds, 10)
          try:
              list(loader)
          except NotImplementedError:
              pass
          else:
              assert False
  
imports: from unittest import TestCase
  import jax.numpy
  import numpy
  import optax
  import pytest
  import elegy
label_desc: Use image node_id 3 for calling the DataLoaderTestCase obj's underlying member method code with example usage: obj.test_not_implemented_ds() and returns: int