Hey, how i can build a simple vector

from llama_index import VectorStoreIndex, ServiceContext
from llama_index.llms import Ollama
from llama_index.embeddings import OllamaEmbedding

llm = llm = Ollama(model="llama2", request_timeout=60.0)
embed_model = OllamaEmbedding(
    model_name="llama2",
    base_url="http://localhost:11434",
    ollama_additional_kwargs={"mirostat": 0},
)

service_context = ServiceContext.from_defaults(llm=llm, embed_model=embed_model)
set_global_service_context(service_context)


index = VectorStoreIndex.from_documents(documents)