code: def sigma2fwhm(sigma):
      
      sigma = np.asarray(sigma)
      return np.sqrt(8 * np.log(2)) * sigma
docs: Convert a sigma in a Gaussian kernel to a FWHM value.
  
      Parameters
      ----------
      sigma: float or numpy.array
         sigma value or values
  
      Returns
      -------
      fwhm: float or numpy.array
         fwhm values corresponding to `sigma` values