class_docstr: A BlockList that submits tasks lazily on-demand.
  
  This BlockList is used for implementing read operations (e.g., to avoid
  needing to read all files of a Dataset when the user is just wanting to
  .take() the first few rows or view the schema).
class_docstr_tok: ["A","BlockList","that","submits","tasks","lazily","on-demand",".","This","BlockList","is","used","for","implementing","read","operations","(","e.g.",",","to","avoid","needing","to","read","all","files","of","a","Dataset","when","the","user","is","just","wanting","to",".take","(",")","the","first","few","rows","or","view","the","schema",")","."]
docstr: Iterate over the block futures and their corresponding metadata futures.
  
  This does NOT block on the execution of each submitted task.
code: def _iter_block_partition_refs(
      self,
  ) -> Iterator[
      Tuple[
          ObjectRef[MaybeBlockPartition],
          Union[None, ObjectRef[BlockMetadata]],
      ]
  ]:
      """Iterate over the block futures and their corresponding metadata futures.
  
      This does NOT block on the execution of each submitted task.
      """
      outer = self
  
      class Iter:
          def __init__(self):
              self._pos = -1
  
          def __iter__(self):
              return self
  
          def __next__(self):
              self._pos += 1
              if self._pos < len(outer._tasks):
                  return outer._get_or_compute(self._pos)
              raise StopIteration
  
      return Iter()
  
imports: import math
  import uuid
  from typing import Any, Dict, Iterable, Iterator, List, Optional, Tuple, Union
  import ray
  from ray.data._internal.block_list import BlockList
  from ray.data._internal.memory_tracing import trace_allocation
  from ray.data._internal.progress_bar import ProgressBar
  from ray.data._internal.remote_fn import cached_remote_fn
  from ray.data._internal.stats import DatasetStats, _get_or_create_stats_actor
  from ray.data._internal.util import _split_list
  from ray.data.block import Block, BlockAccessor, BlockExecStats, BlockMetadata, BlockPartitionMetadata, MaybeBlockPartition
  from ray.data.context import DataContext
  from ray.data.datasource import ReadTask
  from ray.types import ObjectRef
label_desc: Use image node_id 22 for calling the LazyBlockList obj's underlying member method code with example usage: obj._iter_block_partition_refs() and returns: Iter, self, outer