code: def test_sigma_fwhm():
      # ensure that fwhm2sigma and sigma2fwhm are inverses of each other
      fwhm = np.arange(1.0, 5.0, 0.1)
      sigma = np.arange(1.0, 5.0, 0.1)
      assert np.allclose(sigma2fwhm(fwhm2sigma(fwhm)), fwhm)
      assert np.allclose(fwhm2sigma(sigma2fwhm(sigma)), sigma)
  
file_path: nipy/nipy/algorithms/tests/test_kernel_smooth.py
imports: import numpy
  import pytest
  from numpy.random import randint
  from numpy.testing import assert_array_almost_equal
  from transforms3d.taitbryan import euler2mat
  from ...None import load_image
  from ...core.api import AffineTransform, Image, compose, drop_io_dim
  from ...testing import anatfile, funcfile
  from ..kernel_smooth import LinearFilter, fwhm2sigma, sigma2fwhm
label_desc: Use image node_id 4 for calling a global function with example usage: test_sigma_fwhm() without return types