class_docstr: Combo Faiss Retrieval Flask resource.
  The PUT method is to get KNN tokens, add new chunks, reset index.
code: def update_weights(self, weights):
      weights = np.array(weights)
      # normalize the weights
      weights = weights / weights.sum()
      self.weight_container[0] = weights
  
imports: import pickle
  import threading
  from typing import List, Union
  import faiss
  import numpy
  import torch
  from flask import Flask, jsonify, request
  from flask_restful import Api, Resource
  from nemo.collections.common.tokenizers.tokenizer_spec import TokenizerSpec
  from nemo.collections.nlp.modules.common.megatron.retrieval_services.retrieval_service import DynamicFaissRetrievalService, FaissRetrievalService
  from nemo.collections.nlp.modules.common.megatron.retrieval_services.util import lock
label_desc: Use image node_id 4 for calling the ComboRetrievalResource obj's underlying member method code with example usage: obj.update_weights(weights) without return types