code: def test_op_propagates_errors(self, num_examples: int) -> None:
      def fn(d: int) -> int:
          if d == 60:
              raise ValueError("map error")
  
          return d
  
      seq = list(range(1, 100))
  
      pipeline = (
          read_sequence(seq).map(fn).prefetch(num_examples).and_return()
      )
  
      with pytest.raises(DataPipelineError) as exc_info:
          for d in pipeline:
              pass
  
      cause = exc_info.value.__cause__
  
      assert isinstance(cause, ValueError)
  
      assert str(cause) == "map error"
  
file_path: fairseq2/tests/unit/data/data_pipeline/test_prefetch.py
imports: from itertools import islice
  import pytest
  from fairseq2.data import DataPipelineError, read_sequence
label_desc: Use image node_id 4 for calling the TestPrefetchOp obj's underlying member method code with example usage: obj.test_op_propagates_errors(num_examples) and returns: d