code: def require_distributed_retrieval(test_case):
      """
      Decorator marking a test that requires a set of dependencies necessary for pefrorm retrieval with
      :class:`~transformers.RagRetriever`.
  
      These tests are skipped when respective libraries are not installed.
  
      """
      if not (
          is_datasets_available()
          and is_faiss_available()
          and is_psutil_available()
      ):
          test_case = unittest.skip(
              "test requires Datasets, Faiss, psutil"
          )(test_case)
      return test_case
  
imports: import json
  import os
  import shutil
  import sys
  import tempfile
  import unittest
  from unittest import TestCase
  from unittest.mock import patch
  import numpy
  from datasets import Dataset
  import faiss
  from transformers import BartConfig, BartTokenizer, DPRConfig, DPRQuestionEncoderTokenizer, RagConfig
  from transformers.file_utils import is_datasets_available, is_faiss_available, is_psutil_available, is_torch_available
  from transformers.integrations import is_ray_available
  from transformers.models.bert.tokenization_bert import VOCAB_FILES_NAMES
  from transformers.models.rag.retrieval_rag import CustomHFIndex, RagRetriever
  from transformers.models.roberta.tokenization_roberta import VOCAB_FILES_NAMES
  from transformers.testing_utils import require_ray
label_desc: Use image node_id 1 for calling a global function with example usage: require_distributed_retrieval(test_case) and returns: test_case