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: cluster_tool_append.m
    path of file: ./repos/CanlabCore/CanlabCore/Cluster_contig_region_tools/cluster_tool
    
    the code of the file until where you have to start completion: function varargout = cluster_tool_append(varargin)
%CLUSTER_TOOL_APPEND M-file for cluster_tool_append.fig
%      CLUSTER_TOOL_APPEND, by itself, creates a new CLUSTE
    
function named CALLBACK in CLUSTER_TOOL_APPEND.M with the given input
%      arguments.
%
%      *See GUI Options on GUIDE's Tools menu.  Choose "GUI allows only one
%      instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES

% Edit the above text to modify the response to help cluster_tool_append

% Last Modified by GUIDE v2.5 13-Jul-2006 21:50:10

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @cluster_tool_append_OpeningFcn, ...
                   'gui_OutputFcn',  @cluster_tool_append_OutputFcn, ...
                   'gui_LayoutFcn',  [], ...
                   'gui_Callback',   []);
if nargin && ischar(varargin{1})
   gui_State.gui_Callback = str2func(varargin{1});
end