code: def test_is_proxy():
      # Test is_proxy function
      hdr = FunkyHeader((2, 3, 4))
      bio = BytesIO()
      prox = ArrayProxy(bio, hdr)
      assert is_proxy(prox)
      assert not is_proxy(bio)
      assert not is_proxy(hdr)
      assert not is_proxy(np.zeros((2, 3, 4)))
  
      class NP:
          is_proxy = False
  
      assert not is_proxy(NP())
  
imports: import contextlib
  import gzip
  import pickle
  from io import BytesIO
  from unittest import mock
  import numpy
  import pytest
  from numpy.testing import assert_array_almost_equal, assert_array_equal
  from packaging.version import Version
  from ..None import __version__
  from ..arrayproxy import ArrayProxy, get_obj_dtype, is_proxy, reshape_dataobj
  from ..deprecator import ExpiredDeprecationError
  from ..nifti1 import Nifti1Header, Nifti1Image
  from ..openers import ImageOpener
  from ..testing import memmap_after_ufunc
  from ..tmpdirs import InTemporaryDirectory
  from .test_fileslice import slicer_samples
  from .test_openers import patch_indexed_gzip
label_desc: Use image node_id 9 for calling a global function with example usage: test_is_proxy() without return types