code: def test_optional_type_hint():
      class MyExec(Executor):
          @requests
          def foo(self, docs: Optional[DocumentArray], **kwargs):
              return docs
  
      with Flow().add(uses=MyExec) as f:
          f.post("/", inputs=Document())
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_optional_type_hint() and returns: docs