How to use the specutils.analysis.centroid function in specutils

This is a helper function for the above `gaussian_sigma_width()` method.
    """

    if regions is not None:
        calc_spectrum = extract_region(spectrum, regions)
    else:
        calc_spectrum = spectrum

    if hasattr(spectrum, 'mask') and spectrum.mask is not None:
        flux = calc_spectrum.flux[~spectrum.mask]
        spectral_axis = calc_spectrum.spectral_axis[~spectrum.mask]
    else:
        flux = calc_spectrum.flux
        spectral_axis = calc_spectrum.spectral_axis

    centroid_result = centroid(spectrum, regions)

    if flux.ndim > 1:
        spectral_axis = np.broadcast_to(spectral_axis, flux.shape, subok=True)
        centroid_result = centroid_result[:, np.newaxis]

    dx = (spectral_axis - centroid_result)
    sigma = np.sqrt(np.sum((dx * dx) * flux, axis=-1) / np.sum(flux, axis=-1))

    return sigma

        'mean': lambda s: centroid(s, region=None),
        'stddev': lambda s: gaussian_sigma_width(s)

def compute_stats(spectrum):
    """
    Compute basic statistics for a spectral region.
    Parameters
    ----------
    spectrum : `~specutils.spectra.spectrum1d.Spectrum1D`
    region: `~specutils.utils.SpectralRegion`
    """

    try:
        cent = centroid(spectrum, region=None) # we may want to adjust this for continuum subtraction
    except Exception as e:
        logging.debug(e)
        cent = "Error"

    try:
        snr_val = snr(spectrum)
    except Exception as e:
        logging.debug(e)
        snr_val = "N/A"

    try:
        fwhm_val = fwhm(spectrum)
    except Exception as e:
        logging.debug(e)
        fwhm_val = "Error"