что делает этот код:

from llama_index import (
    GPTVectorStoreIndex, SimpleDirectoryReader, PromptHelper, LLMPredictor,
    ServiceContext,
)
from langchain import OpenAI
from dotenv import load_dotenv


def construct_index(directory_path):
    max_input_size = 1024
    num_outputs = 256
    max_chunk_overlap = 20
    chunk_size_limit = 600

    prompt_helper = PromptHelper(
        max_input_size,
        num_outputs,
        max_chunk_overlap,
        chunk_size_limit=chunk_size_limit
    )

    llm_predictor = LLMPredictor(llm=OpenAI(
        temperature=0.5,
        model_name="text-davinci-003",
        max_tokens=num_outputs
    ))

    documents = SimpleDirectoryReader(directory_path).load_data()

    service_context = ServiceContext.from_defaults(
        llm_predictor=llm_predictor,
        prompt_helper=prompt_helper
    )
    index = GPTVectorStoreIndex.from_documents(
        documents,
        service_context=service_context
    )

    return index

load_dotenv()

index = construct_index('docs')

# index.storage_context.persist('./storage')

query_engine = index.as_query_engine()
response = query_engine.query("процитируй последнее предложение из этого документа")

print(response)
 Write your response using less than 800 words.
user