code: def sigma2fwhm(sigma):
      """Convert a sigma in a Gaussian kernel to a FWHM value
  
      Parameters
      ----------
      sigma : array-like
         sigma value or values
  
      Returns
      -------
      fwhm : array or float
         fwhm values corresponding to `sigma` values
  
      Examples
      --------
      >>> fwhm = sigma2fwhm(3)
      >>> fwhms = sigma2fwhm([3, 4, 5])
      >>> fwhm == fwhms[0]
      True
      """
      return np.asarray(sigma) * SIGMA2FWHM
  
file_path: nibabel/nibabel/processing.py
imports: import numpy
  import numpy.linalg
  from .optpkg import optional_package
  from .affines import AffineError, append_diag, from_matvec, rescale_affine, to_matvec
  from .imageclasses import spatial_axes_first
  from .nifti1 import Nifti1Image
  from .orientations import axcodes2ornt, io_orientation, ornt_transform
  from .spaces import vox2out_vox
label_desc: Use image node_id 2 for calling a global function with example usage: sigma2fwhm(sigma) and returns: unknown