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: meshVertexClustering.m
    path of file: ./repos/matGeom/matGeom/meshes3d
    
    the code of the file until where you have to start completion: function varargout = meshVertexClustering(vertices, faces, spacing, varargin)
%MESHVERTEXCLUSTERING Simplifies a mesh using vertex clustering.
%
%   [V2, F2] = meshVertexClustering(V, F, SPACING)
%   [V2, F2] = meshVertexClustering(MESH, SPACING)
%   MESH2 = meshVertexClustering(...)
%
%   Simplifies a mesh using vertex clustering. Input mesh is specified
%   either by a pair V, F containing the vertex coordinates and the faces

    
function varargout = meshVertexClustering(vertices, faces, spacing, varargin)
%MESHVERTEXCLUSTERING Simplifies a mesh using vertex clustering.
%
%   [V2, F2] = meshVertexClustering(V, F, SPACING)
%   [V2, F2] = meshVertexClustering(MESH, SPACING)
%   MESH2 = meshVertexClustering(...)
%
%   Simplifies a mesh using vertex clustering. Input mesh is specified
%   either by a pair V, F containing the vertex coordinates and the faces
%   informations, or by a structure with fields 'vertices' and 'faces'.
%
%   The SPACING input defines the size of the grid. It can be either a
%   scalar (uniform grid) or a 1-by-3 row vector. 
%
%   The output is specified either in two outputs, or in a structure with
%   fields 'vertices' and 'faces'.
%
%   Example
%     [x, y, z]  = meshgrid(1:100, 1:100, 1:100);
%     img = hypot3(x-51.12, y-52.23, z-53.34);
%     [faces, vertices] = isosurface(img, 45);
%     [v2, f2] = meshVertexClustering(vertices, faces, 10);
%     figure; axis equal; axis([0 100 0 100 0 100]);
%     drawMesh(v2, f2);
%
%   See also 
%     reducepatch, smoothMesh

% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2019-01-28, using Matlab 9.5.0.944444 (R2018b)
% Copyright 2019-2023 INRA - Cepia Software Platform

%% Initialisation

if isstruct(vertices)
    if nargin > 2
        varargin = [{spacing} varargin(:)];
    end