code: def test_prefetch(self):
      ds = DS0()
  
      loader = elegy.data.DataLoader(
          ds, batch_size=2, n_workers=4, shuffle=False, prefetch=3
      )
      batches = list(loader)
      assert len(loader) == len(batches)
  
imports: from unittest import TestCase
  import jax.numpy
  import numpy
  import optax
  import pytest
  import elegy
label_desc: Use image node_id 8 for calling the DataLoaderTestCase obj's underlying member method code with example usage: obj.test_prefetch() without return types