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: find.m
    path of file: ./repos/CBIG/external_packages/matlab/non_default_packages/cifti-matlab-WashU-gradient/@xmltree
    
    the code of the file until where you have to start completion: function list = find(varargin)
% XMLTREE/FIND Find elements in a tree with specified characteristics
% FORMAT list = find(varargin)
%
% tree  - XMLTree object
% xpath - string path with specific grammar (XPath)
% uid   - lists of root uid's
% parameter/value - pair of pattern
% list  - list of uid's of matched elements
%
%      list = find(tree,xpath)
%      list = find(tree,parameter,value[,parameter,value])
%      list = find(tree,uid,parameter,value[,parameter,value])
%
% Grammar for addressing parts of an XML document: 
%        XML Path Language XPath (http://www.w3.org/TR/xpath)
% Example: /element1//element2[1]/element3[5]/element4
%__________________________________________________________________________
%
% Find elements in an XML tree with specified characteristics or given
% a path (using a subset of XPath language).
%__________________________________________________________________________
% Copyright (C) 2002-2011  http://www.artefact.tk/

% Guillaume Flandin
% $Id: find.m 4460 2011-09-05 14:52:16Z guillaume $


    
function list = find(varargin)
% XMLTREE/FIND Find elements in a tree with specified characteristics
% FORMAT list = find(varargin)
%
% tree  - XMLTree object
% xpath - string path with specific grammar (XPath)
% uid   - lists of root uid's
% parameter/value - pair of pattern
% list  - list of uid's of matched elements
%
%      list = find(tree,xpath)
%      list = find(tree,parameter,value[,parameter,value])
%      list = find(tree,uid,parameter,value[,parameter,value])
%
% Grammar for addressing parts of an XML document: 
%        XML Path Language XPath (http://www.w3.org/TR/xpath)
% Example: /element1//element2[1]/element3[5]/element4
%__________________________________________________________________________
%
% Find elements in an XML tree with specified characteristics or given
% a path (using a subset of XPath language).
%__________________________________________________________________________
% Copyright (C) 2002-2011  http://www.artefact.tk/

% Guillaume Flandin
% $Id: find.m 4460 2011-09-05 14:52:16Z guillaume $

% TODO:
%   - clean up subroutines
%   - find should only be documented using XPath (other use is internal)
%   - handle '*', 'last()' in [] and '@'
%   - if a key is invalid, should rather return [] than error ?

if nargin==0
    error('[XMLTree] A tree must be provided');
elseif nargin==1
    list = 1:length(tree.tree);
    return
elseif mod(nargin,2)
    list = sub_find_subtree1(varargin{1}.tree,root(varargin{1}),varargin{2:end