code: def __enter__(
      self,
  ) -> (
      optuna.storages.InMemoryStorage
      | optuna.storages._CachedStorage
      | optuna.storages.RDBStorage
      | optuna.storages.JournalStorage
      | "optuna.integration.DaskStorage"
  ):
      if self.storage_specifier == "inmemory":
          if len(self.extra_args) > 0:
              raise ValueError(
                  "InMemoryStorage does not accept any arguments!"
              )
          return optuna.storages.InMemoryStorage()
      elif "sqlite" in self.storage_specifier:
          self.tempfile = NamedTemporaryFilePool().tempfile()
          url = "sqlite:///{}".format(self.tempfile.name)
          rdb_storage = optuna.storages.RDBStorage(
              url,
              engine_kwargs={
                  "connect_args": {"timeout": SQLITE3_TIMEOUT}
              },
              **self.extra_args,
          )
          return (
              optuna.storages._CachedStorage(rdb_storage)
              if "cached" in self.storage_specifier
              else rdb_storage
          )
      elif self.storage_specifier == "journal_redis":
          journal_redis_storage = optuna.storages.JournalRedisStorage(
              "redis://localhost"
          )
          journal_redis_storage._redis = self.extra_args.get(
              "redis", fakeredis.FakeStrictRedis()  # type: ignore[no-untyped-call]
          )
          return optuna.storages.JournalStorage(journal_redis_storage)
      elif "journal" in self.storage_specifier:
          self.tempfile = NamedTemporaryFilePool().tempfile()
          file_storage = JournalFileStorage(self.tempfile.name)
          return optuna.storages.JournalStorage(file_storage)
      elif self.storage_specifier == "dask":
          self.dask_client = distributed.Client()  # type: ignore[no-untyped-call]
  
          return optuna.integration.DaskStorage(
              client=self.dask_client, **self.extra_args
          )
      else:
          assert False
  
file_path: optuna/optuna/testing/storages.py
imports: from __future__ import annotations
  import sys
  from types import TracebackType
  from typing import Any
  from typing import IO
  import fakeredis
  import pytest
  import optuna
  from optuna.storages import JournalFileStorage
  from optuna.testing.tempfile_pool import NamedTemporaryFilePool
label_desc: Use image node_id 2 for calling the StorageSupplier obj's underlying member method code with example usage: obj.__enter__() and returns: optuna, unknown, optuna, optuna, optuna