code: def fwhm2sigma(fwhm):
      """Convert a FWHM value to sigma in a Gaussian kernel.
  
      Parameters
      ----------
      fwhm : array-like
         FWHM value or values
  
      Returns
      -------
      sigma : array or float
         sigma values corresponding to `fwhm` values
  
      Examples
      --------
      >>> sigma = fwhm2sigma(6)
      >>> sigmae = fwhm2sigma([6, 7, 8])
      >>> sigma == sigmae[0]
      True
      """
      fwhm = np.asarray(fwhm)
      return fwhm / np.sqrt(8 * np.log(2))
  
file_path: nipy/nipy/algorithms/kernel_smooth.py
imports: import gc
  import numpy
  import numpy.linalg
  from numpy import fft
  from nipy.core.api import AffineTransform, Image
  from nipy.core.reference.coordinate_map import product
  from nipy.utils import seq_prod
label_desc: Use image node_id 1 for calling a global function with example usage: fwhm2sigma(fwhm) and returns: unknown