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_file_merge.m
    path of file: ./repos/malini/Codes/deconvolution - model/spm8
    
    the code of the file until where you have to start completion: function V4 = spm_file_merge(V,fname,dt)
% Concatenate 3D volumes into a single 4D volume
% FUNCTION V4 = spm_file_merge(V,fname,dt)
% V      - images to concatenate (char array or spm_vol struct)
% fname  - filename for output 4D volume [defaults: '4D.nii']
%          Unless explicit, output folder is the one containing first image
% dt     - datatype (see spm_type) [defaults: 0]
%          0 means same datatype than first input volume
%
% V4     - spm_vol struct of the 4D volume
%__________________________________________________________________________
%
% For integer datatypes, the file scale factor is chosen as to maximise
% the range of admissible values. This may lead to quantization error
% differences between the input and output images values.
%__________________________________________________________________________
% Copyright (C) 2009 Wellcome Trust Centre for Neuroimaging

% John Ashburner

    
function V4 = spm_file_merge(V,fname,dt)
% Concatenate 3D volumes into a single 4D volume
% FUNCTION V4 = spm_file_merge(V,fname,dt)
% V      - images to concatenate (char array or spm_vol struct)
% fname  - filename for output 4D volume [defaults: '4D.nii']
%          Unless explicit, output folder is the one containing first image
% dt     - datatype (see spm_type) [defaults: 0]
%          0 means same datatype than first input volume
%
% V4     - spm_vol struct of the 4D volume
%__________________________________________________________________________
%
% For integer datatypes, the file scale factor is chosen as to maximise
% the range of admissible values. This may lead to quantization error
% differences between the input and output images values.
%__________________________________________________________________________
% Copyright (C) 2009 Wellcome Trust Centre for Neuroimaging

% John Ashburner
% $Id: spm_file_merge.m 5041 2012-11-07 16:40:01Z guillaume $

%-Input: V
%--------------------------------------------------------------------------
if ~nargin
    V = spm_select([1 Inf],'image','Select images to concatenate');
end