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_cfg_eeg_crop.m
    path of file: ./repos/spm/config
    
    the code of the file until where you have to start completion: function crop = spm_cfg_eeg_crop
% configuration file for cropping M/EEG data
%__________________________________________________________________________

% Vladimir Litvak
% Copyright (C) 2009-2022 Wellcome Centre for Human Neuroimaging


%--------------------------------------------------------------------------
% crop
%--------------------------------------------------------------------------
crop          = cfg_exbranch;
crop.tag      = 'crop';
crop.name     = 'Crop';
crop.val      = @crop_cfg;
crop.help     = {'Cropping M/EEG data'}';
crop.prog     = @eeg_crop;
crop.vout     = @vout_eeg_crop;
crop.modality = {'EEG'};


%==========================================================================
function varargout = crop_cfg

persistent cfg
if ~isempty(cfg), varargout = {cfg}; return; end

%--------------------------------------------------------------------------
% D
%--------------------------------------------------------------------------
D        = cfg_files;
D.tag    = 'D';
D.name   = 'File Name';
D.filter = 'mat';
D.num    = [1 1];
D.help   = {'Select the M/EEG mat file.'};

%--------------------------------------------------------------------------
% timewin
%--------------------------------------------------------------------------
timewin         = cfg_entry;
timewin.tag     = 'timewin';
timewin.name    = 'Time window';
timewin.help    = {'Start and stop of the time window [ms].'};
timewin.strtype = 'r';
timewin.num     = [1 2];
timewin.val     = {[-Inf Inf]};

%--------------------------------------------------------------------------
% freqwin
%--------------------------------------------------------------------------
freqwin         = cfg_entry;
freqwin.tag     = 'freqwin';
freqwin.name    = 'Frequency window';
freqwin.help    = {'Start and stop of the frequency window (Hz).'};
freqwin.strtype = 'r';
freqwin.num     = [1 2];
freqwin.val     = {[-Inf Inf]};

%--------------------------------------------------------------------------
% prefix
%--------------------------------------------------------------------------
prefix         = cfg_entry;
prefix.tag     = 'prefix';
prefix.name    = 'Filename Prefix';
prefix.help    = {'Specify the string to be prepended to the filenames of the output dataset. Default prefix is ''p''.'};
prefix.strtype = 's';
prefix.num     = [1 Inf];
prefix.val     = {'p'};

[cfg,varargout{1}] = deal({D, timewin, freqwin, spm_cfg_eeg_channel_selector, prefix});


%==========================================================================
function out = eeg_crop(job)
% construct the S struct
S           = job;
S.D         = S.D{1};
S.channels  = spm_cfg_eeg_channel_selector(job.channels);
out.D       = spm_eeg_crop(S);

    
function crop = spm_cfg_eeg_crop
% configuration file for cropping M/EEG data
%__________________________________________________________________________

% Vladimir Litvak
% Copyright (C) 2009-2022 Wellcome Centre for Human Neuroimaging


%--------------------------------------------------------------------------
% crop
%--------------------------------------------------------------------------
crop          = cfg_exbranch;
crop.tag      = 'crop';
crop.name     = 'Crop';
crop.val      = @crop_cfg;
crop.help     = {'Cropping M/EEG data'}';
crop.prog     = @eeg_crop;
crop.vout     = @vout_eeg_crop;
crop.modality = {'EEG'};


%==========================================================================
function varargout = crop_cfg

persistent cfg
if ~isempty(cfg), varargout = {cfg}; return; end

%--------------------------------------------------------------------------
% D
%--------------------------------------------------------------------------
D        = cfg_files;
D.tag    = 'D';
D.name   = 'File Name';
D.filter = 'mat';
D.num    = [1 1];
D.help   = {'Select the M/EEG mat file.'};

%--------------------------------------------------------------------------
% timewin
%--------------------------------------------------------------------------
timewin         = cfg_entry;
timewin.tag     = 'timewin';
timewin.name    = 'Time window';
timewin.help    = {'Start and stop of the time window [ms].'};
timewin.strtype = 'r';
timewin.num     = [1 2];
timewin.val     = {[-Inf Inf]};

%--------------------------------------------------------------------------
% freqwin
%--------------------------------------------------------------------------
freqwin         = cfg_entry;
freqwin.tag     = 'freqwin';
freqwin.name    = 'Frequency window';
freqwin.help    = {'Start and stop of the frequency window (Hz).'};
freqwin.strtype = 'r';
freqwin.num     = [1 2];
freqwin.val     = {[-Inf Inf]};

%--------------------------------------------------------------------------
% prefix
%--------------------------------------------------------------------------
prefix         = cfg_entry;
prefix.tag     = 'prefix';
prefix.name    = 'Filename Prefix';
prefix.help    = {'Specify the string to be prepended to the filenames of the output dataset. Default prefix is ''p''.'};
prefix.strtype = 's';
prefix.num     = [1 Inf];
prefix.val     = {'p'};

[cfg,varargout{1}] = deal({D, timewin, freqwin, spm_cfg_eeg_channel_selector, prefix});


%==========================================================================
function out = eeg_crop(job)
% construct the S struct
S           = job;
S.D         = S.D{1};
S.channels  = spm_cfg_eeg_channel_selector(job.channels);
out.D       = spm_eeg_crop(S);
out.Dfname  = {fullfile(out.D)};

%==========================================================================
function dep = vout_eeg_crop(job)
% return depend