code: def test_shards():
      f = Flow().add(uses=SimpleAddExecutor, shards=2)
  
      with f:
          docs = f.post(on="/index", inputs=[Document(text="1")])
          assert len(docs) == 2
  
imports: from docarray import Document, DocumentArray
  from jina import Executor, Flow, requests
  import pytest
label_desc: Use image node_id 3 for calling a global function with example usage: test_shards() without return types