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: cs_demo3.m
    path of file: ./repos/SuiteSparse/CSparse/MATLAB/Demo
    
    the code of the file until where you have to start completion: function cs_demo3 (do_pause, matrixpath)
%CS_DEMO3 MATLAB version of the CSparse/Demo/cs_demo3.c program.
%   Cholesky update/downdate.
%
% Example:
%   cs_demo3
% See also: cs_demo

% CSparse, Copyright (c) 2006-2022, Timothy A. Davis. All Rights Reserved.
% SPDX-License-Identifier: LGPL-2.1+


    
function cs_demo3 (do_pause, matrixpath)
%CS_DEMO3 MATLAB version of the CSparse/Demo/cs_demo3.c program.
%   Cholesky update/downdate.
%
% Example:
%   cs_demo3
% See also: cs_demo

% CSparse, Copyright (c) 2006-2022, Timothy A. Davis. All Rights Reserved.
% SPDX-License-Identifier: LGPL-2.1+

if (nargin < 2)
    matrixpath = [] ;
end

if (isempty (matrixpath))
    try
        % older versions of MATLAB do not have an input argument to mfilename
        p = mfilename ('fullpath') ;
        t = strfind (p, '/') ;
        matrixpath = [ p(1:t(end