code: def _check_if_crashed(self) -> None:
      if self.is_crashed:
          raise RuntimeError("The backend is down")
  
imports: from typing import Any
  from typing import Type
  from syft.serde.serializable import serializable
  from syft.store.document_store import DocumentStore
  from syft.store.document_store import PartitionSettings
  from syft.store.document_store import StoreConfig
  from syft.store.kv_document_store import KeyValueBackingStore
  from syft.types.syft_object import SyftObject
  from syft.types.uid import UID
label_desc: Use image node_id 2 for calling the MockKeyValueBackingStore obj's underlying member method code with example usage: obj._check_if_crashed() without return types