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/spm12
    
    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 con_image = spm_bms_compare_groups(BMSfiles,name,contrast)
%

    
function con_image = spm_bms_compare_groups(BMSfiles,name,contrast)
% Compare BMS maps for different groups
% FORMAT con_image = spm_bms_compare_groups(BMSfiles,name,contrast)
%
% 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) 2009-2019 Wellcome Trust Centre for Neuroimaging

% Maria Joao Rosa
% $Id: spm_bms_compare_groups.m 7577 2019-04-24 08:59:56Z 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