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: montage_clusters_text.m
    path of file: ./repos/CanlabCore/CanlabCore/Visualization_functions
    
    the code of the file until where you have to start completion: function montage_clusters_text(ovl,clusters,varargin)
% :Inputs:
%
%   **varargin:**
%        additional clusters structures
%        this function puts text cluster numbers on cluster centers
%
%   **color:**
%        cell array of text strings indicating colors {'r' 'g'} etc...
%
% ..
%    Tor Wager
% ..

if isempty(ovl), ovl = which
    
function index = plot_cluster(clusters,oimg,rc,V,whsl,myc,textx,texty,clind,odims,varargin)
% var argument is list of centers, x y z are rows, cols are coords

XYZmm = cat(2,clusters.XYZmm);
XYZ = mm2voxel(XYZmm,V)';

% text numbers, if plotting text at xyz coords of centers (varargin)
if length(varargin) > 0
    cencoo = varargin{1};
    cencoo = mm2voxel(cencoo,V)';
    centext = varargin{2};
    %cenind = 1;
end