code: def get_dummy_retriever(self):
      retriever = RealmRetriever(
          block_records=self.get_dummy_block_records(),
          tokenizer=self.get_tokenizer(),
      )
      return retriever
  
imports: import os
  import shutil
  import tempfile
  from unittest import TestCase
  from unittest.mock import patch
  import numpy
  from datasets import Dataset
  from transformers.models.realm.configuration_realm import RealmConfig
  from transformers.models.realm.retrieval_realm import _REALM_BLOCK_RECORDS_FILENAME, RealmRetriever
  from transformers.models.realm.tokenization_realm import VOCAB_FILES_NAMES, RealmTokenizer
label_desc: Use image node_id 7 for calling the RealmRetrieverTest obj's underlying member method code with example usage: obj.get_dummy_retriever() and returns: retriever