You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: spm_sextract.m
    path of file: ./repos/malini/Codes/deconvolution - model/spm8/toolbox/SRender
    
    the code of the file until where you have to start completion: function out = spm_sextract(job)
% Surface extraction

    
function out = spm_sextract(job)
% Surface extraction
%_______________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging

% John Ashburner
% $Id: spm_sextract.m 2210 2008-09-26 20:14:13Z john $

images = job.images;
Vi     = spm_vol(strvcat(images));
n      = numel(Vi);                %-#images
if n==0, error('no input images specified'), end