Persist VectorStoreIndex (LlamaIndex) locally

Question

I am trying to run this

import logging
import sys
from llama_index import VectorStoreIndex, SimpleDirectoryReader, ServiceContext
import torch
from llama_index.llms import LlamaCPP
from llama_index.llms.llama_utils import messages_to_prompt, completion_to_prompt
from langchain.embeddings import HuggingFaceEmbeddings
from llama_index.embeddings import LangchainEmbedding
from llama_index import ServiceContext, set_global_service_context

logging.basicConfig(stream=sys.stdout, level=logging.INFO)
logging.getLogger().addHandler(logging.StreamHandler(stream=sys.stdout))

llm = LlamaCPP(
    model_url='https://huggingface.co/TheBloke/Mistral-7B-Instruct-v0.1-GGUF/resolve/main/mistral-7b-instruct-v0.1.Q4_K_M.gguf',
    model_path=None,
    temperature=0.1,
    max_new_tokens=256,
    context_window=3900,
    generate_kwargs={},
    model_kwargs={"n_gpu_layers": -1},
    messages_to_prompt=messages_to_prompt,
    completion_to_prompt=completion_to_prompt,
    verbose=True,
)

embed_model = LangchainEmbedding(
  HuggingFaceEmbeddings(model_name="thenlper/gte-large")
)

service_context = ServiceContext.from_defaults(
    chunk_size=256,
    llm=llm,
    embed_model=embed_model
)

documents = SimpleDirectoryReader("/content/Data/").load_data()

index = VectorStoreIndex.from_documents(documents, service_context=service_context)

Can someone help me persist the index locally so I don't have to redo this every time?

Tried doing this way, throwing an error -

from llama_index import StorageContext, load_index_from_storage
index.storage_context.persist("/content/pers")
storage_context2 = StorageContext.from_defaults(persist_dir="/content/pers")
new_index2 = load_index_from_storage(storage_context2)
new_query_engine2 = new_index2.as_query_engine()

ValueError Traceback (most recent call last) /usr/local/lib/python3.10/dist-packages/llama_index/llms/utils.py in resolve_llm(llm) 28 llm = OpenAI() ---> 29 validate_openai_api_key(llm.api_key) 30 except ValueError as e:

8 frames ValueError: No API key found for OpenAI. Please set either the OPENAI_API_KEY environment variable or openai.api_key prior to initialization. API keys can be found or created at https://platform.openai.com/account/api-keys

During handling of the above exception, another exception occurred:

ValueError Traceback (most recent call last) /usr/local/lib/python3.10/dist-packages/llama_index/llms/utils.py in resolve_llm(llm) 29 validate_openai_api_key(llm.api_key) 30 except ValueError as e: ---> 31 raise ValueError( 32 "\n******\n" 33 "Could not load OpenAI model. "

ValueError:

---

Could not load OpenAI model. If you intended to use OpenAI, please check your OPENAI_API_KEY. Original error: No API key found for OpenAI. Please set either the OPENAI_API_KEY environment variable or openai.api_key prior to initialization. API keys can be found or created at https://platform.openai.com/account/api-keys

To disable the LLM entirely, set llm=None.

---

I am new to this, any help will be much appreciated. Thanks in advance.