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: Get the metadata for all blocks.
code: def get_metadata(
      self, fetch_if_missing: bool = False
  ) -> List[BlockMetadata]:
      """Get the metadata for all blocks."""
      if all(meta is not None for meta in self._cached_metadata):
          # Always return fetched metadata if we already have it.
          metadata = self._flatten_metadata(self._cached_metadata)
      elif not fetch_if_missing:
          metadata = [
              m if m is not None else [t.get_metadata()]
              for m, t in zip(self._cached_metadata, self._tasks)
          ]
          metadata = self._flatten_metadata(metadata)
      else:
          _, metadata = self._get_blocks_with_metadata()
      return metadata
  
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 3 for calling the LazyBlockList obj's underlying member method code with example usage: obj.get_metadata(fetch_if_missing) and returns: metadata