class_docstr: :class:`DatasetVersion` has two constructors: :func:`.from_json` and
  :func:`.get_region`.
  
  Parameters
  ----------
  url : :obj:`dict` or :obj:`str`
      Nested dictionary of URLs containing key: value pairs, like
      ``cloud: {region: url}`` if using :func:`.from_json` constructor,
      or a string with the URL from appropriate region if using the
      :func:`.get_region` constructor.
  version : :obj:`str`, optional
      String of dataset version, if not ``None``.
  reference_genome : :obj:`str`, optional
      String of dataset reference genome, if not ``None``.
docstr: Find the prefix of the given indexer expression that can index the
  :class:`.DatasetVersion`, if it exists.
  
  Parameters
  ----------
  indexer_key_expr : :class:`StructExpression`
      Row key struct from relational object to be annotated.
  all_matches : :obj:`bool`
      ``True`` if `indexer_key_expr` key is not unique, indicated in
      :attr:`.Dataset.key_properties` for each dataset. If ``True``, value
      of `indexer_key_expr` is array of all matches. If ``False``, there
      will only be single value of expression.
  
  Returns
  -------
  :class:`StructExpression`, optional
      Struct of compatible indexed values, if they exist.
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code: def maybe_index(
      self, indexer_key_expr: StructExpression, all_matches: bool
  ) -> Optional[StructExpression]:
      """Find the prefix of the given indexer expression that can index the
      :class:`.DatasetVersion`, if it exists.
  
      Parameters
      ----------
      indexer_key_expr : :class:`StructExpression`
          Row key struct from relational object to be annotated.
      all_matches : :obj:`bool`
          ``True`` if `indexer_key_expr` key is not unique, indicated in
          :attr:`.Dataset.key_properties` for each dataset. If ``True``, value
          of `indexer_key_expr` is array of all matches. If ``False``, there
          will only be single value of expression.
  
      Returns
      -------
      :class:`StructExpression`, optional
          Struct of compatible indexed values, if they exist.
      """
      return hl.read_table(self.url)._maybe_flexindex_table_by_expr(
          indexer_key_expr, all_matches=all_matches
      )
  
imports: import json
  import os
  import warnings
  from typing import Iterable, List, Optional, Set, Tuple, Union
  import hail
  import pkg_resources
  from hailtop.utils import external_requests_client_session, retry_response_returning_functions
  from .lens import MatrixRows, TableRows
  from ..expr import StructExpression
  from ..matrixtable import MatrixTable, matrix_table_type
  from ..table import Table, table_type
  from ..typecheck import oneof, typecheck_method
  from ..utils.java import Env, info
label_desc: Use image node_id 5 for calling the DatasetVersion obj's underlying member method code with example usage: obj.maybe_index(indexer_key_expr, all_matches) and returns: hl