code: def retrieve(self, question_hidden_states, n_docs):
      doc_ids, retrieved_doc_embeds = self.retriever._main_retrieve(
          question_hidden_states, n_docs
      )
      return doc_ids, retrieved_doc_embeds
  
file_path: transformers/examples/research_projects/rag/distributed_ray_retriever.py
imports: import logging
  import random
  import ray
  from transformers import RagConfig, RagRetriever, RagTokenizer
  from transformers.models.rag.retrieval_rag import CustomHFIndex
label_desc: Use image node_id 4 for calling the RayRetriever obj's underlying member method code with example usage: obj.retrieve(question_hidden_states, n_docs) and returns: doc_ids,  retrieved_doc_embeds