code: def test_str_leak():
      from sys import getrefcount
  
      fmt = "f4"
      pytest.gc_collect()
      start = getrefcount(fmt)
      d = m.dtype_wrapper(fmt)
      assert d is np.dtype("f4")
      del d
      pytest.gc_collect()
      assert getrefcount(fmt) == start
  
imports: import re
  import pytest
  import env
  from pybind11_tests import numpy_dtypes
label_desc: Use image node_id 23 for calling a global function with example usage: test_str_leak() without return types