docstr: Retrieve the top k results for the given query.
  
  If `return_data` is True, returns the data associated with the indices. Otherwise, returns the indices.
code: def search(
      self,
      df,
      backend: "Backend",
      k: int = 10,
      return_data: bool = False,
  ) -> Union[List[int], List[Dict[str, Any]]]:
      """Retrieve the top k results for the given query.
  
      If `return_data` is True, returns the data associated with the indices. Otherwise, returns the indices.
      """
      pass
  
imports: import hashlib
  import json
  import os
  from abc import ABC, abstractmethod
  from typing import Any, Callable, Dict, List, Optional, Type, TYPE_CHECKING, Union
  import numpy
  import pandas
  from tqdm import tqdm
  from ludwig.vector_index import FAISS, get_vector_index_cls
  from ludwig.vector_index.base import VectorIndex
  from ludwig.utils.batch_size_tuner import BatchSizeEvaluator
  from ludwig.utils.torch_utils import get_torch_device
label_desc: Use image node_id 2 for calling the RetrievalModel obj's underlying member method code with example usage: obj.search(df, backend, k, return_data) without return types