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_eeg_inv_check.m
    path of file: ./repos/malini/Codes/deconvolution - model/spm8
    
    the code of the file until where you have to start completion: function [D,val] = spm_eeg_inv_check(varargin)
% Checks that the EEG/MEG .mat file structure is loaded properly and that
% the particular inversion of interest has been specified
%
% FORMAT [D,val] = spm_eeg_inv_check(D,[val])
% Input:
% S              - data structure or its filename
% val            - model of interest (usually 1)
% Output:
% D              - data structure
% val            - model of interest D.val
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging

% Jeremie Mattout, Karl Friston
% $Id: spm_eeg_inv_check.m 2861 2009-03-11 18:41:03Z guillaume $


% Check - prompt for file if necessary

    
function [D,val] = spm_eeg_inv_check(varargin)
% Checks that the EEG/MEG .mat file structure is loaded properly and that
% the particular inversion of interest has been specified
%
% FORMAT [D,val] = spm_eeg_inv_check(D,[val])
% Input:
% S              - data structure or its filename
% val            - model of interest (usually 1)
% Output:
% D              - data structure
% val            - model of interest D.val
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging

% Jeremie Mattout, Karl Friston
% $Id: spm_eeg_inv_check.m 2861 2009-03-11 18:41:03Z guillaume $


% Check - prompt for file if necessary
%--------------------------------------------------------------------------
if nargin == 0
    [D, sts] = spm_select(1, 'mat', 'Select EEG/MEG mat file');
    if ~sts, D = []; val = 0; return; end