code: def test_function_signatures(doc):
      assert (
          doc(m.test_callback3)
          == "test_callback3(arg0: Callable[[int], int]) -> str"
      )
      assert (
          doc(m.test_callback4)
          == "test_callback4() -> Callable[[int], int]"
      )
  
file_path: coremltools/deps/pybind11/tests/test_callbacks.py
imports: import time
  from threading import Thread
  import pytest
  import env
  from pybind11_tests import callbacks
label_desc: Use image node_id 7 for calling a global function with example usage: test_function_signatures(doc) without return types