code: def test_prefetch(protocol, prefetch, num_requests):
      with Flow(protocol=protocol, prefetch=prefetch).add() as f:
          f.post(
              on="/default",
              inputs=DocumentArray.empty(num_requests),
              request_size=1,
          )
  
imports: import pytest
  import requests
  from docarray import DocumentArray
  from jina import Executor, Flow, requests
label_desc: Use image node_id 1 for calling a global function with example usage: test_prefetch(protocol, prefetch, num_requests) without return types