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_bms_compare_groups.m
    path of file: ./repos/ExploreASL/External/SPMmodified
    
    the code of the file until where you have to start completion: function con_image = spm_bms_compare_groups(BMSfiles,name,contrast)
% Compare BMS maps for different groups
% FORMAT spm_bms_compare_groups()
%
% Input (interactive):
% BMS             - BMS.mat files for the two groups to compare
% contrast (name) - name of contrast image that will be save in the current
%                   directory 
% contrast (comp) - comparison between groups. options: 'A>B' (posterior 
%                   probability for group 1 > posterior group 2) 
%                   or 'A<B' (posterior probability group 1 < 
%                   posterior for group 2)
%
% Output: contrast image (path)
%__________________________________________________________________________
% Copyright (C) 2009-2011 Wellcome Trust Centre for Neuroimaging

% Maria Joao Rosa
% $Id: spm_bms_compare_groups.m 4489 2011-09-14 11:27:38Z guillaume $

%-Parameters
%--------------------------------------------------------------------------
if nargin < 3

    
function con_image = spm_bms_compare_groups(BMSfiles,name,contrast)
% Compare BMS maps for different groups
% FORMAT spm_bms_compare_groups()
%
% Input (interactive):
% BMS             - BMS.mat files for the two groups to compare
% contrast (name) - name of contrast image that will be save in the current
%                   directory 
% contrast (comp) - comparison between groups. options: 'A>B' (posterior 
%                   probability for group 1 > posterior group 2) 
%                   or 'A<B' (posterior probability group 1 < 
%                   posterior for group 2)
%
% Output: contrast image (path)
%__________________________________________________________________________
% Copyright (C) 2009-2011 Wellcome Trust Centre for Neuroimaging

% Maria Joao Rosa
% $Id: spm_bms_compare_groups.m 4489 2011-09-14 11:27:38Z guillaume $

%-Parameters
%--------------------------------------------------------------------------
if nargin < 3
    BMSfiles = spm_select(2,'^BMS\.mat$','select BMS.mat files');
    name     = spm_input('Contrast name ? ',1,'s');
    contrast = spm_input('Contrast:','+1','b','A>B|A<B',['A>B';'A<B']);    
end