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: spm_mb_gmm.m
    path of file: ./repos/spm/toolbox/MB
    
    the code of the file until where you have to start completion: function varargout = spm_mb_gmm(varargin)
%
% FORMAT varargout = spm_mb_gmm(varargin)
%__________________________________________________________________________

% John Ashburner
% Copyright (C) 2019-2022 Wellcome Centre for Human Neuroimaging


if nargin>=1 && isa(varargin{1},'char')
    [varargout{1:nargout}] = spm_subfun(localfunctions,varargin{:});
else
    [varargout{1:nargout}] = GMMimages(varargin{:});
end
%==========================================================================

%==========================================================================
functi
    
function lb = marginalsum(SS0, SS1, SS2, m,b,W,nu, O)
% [lb,const] = spm_gmm_lib('marginalsum', SS0, SS1, SS2, m,b, W,nu, O)
%
% SS0       - {1xK}   Zero-th order moment (per config)
% SS1       - {PxK}   First   order moment (per config)
% SS1       - {PxPxK} Second  order moment (per config)
% m         - PxK     Means
% W         - PxPxK   Precision/Scale matrices
% b         - 1xK     Mean degrees of freedom
% nu        - 1xK     Precision degrees of freedom
% O         - Mx1     List of existing codes
%
% lb        -         Sum of (expected) marginal likelihoods
%
% Compute the expected log-likelihood of each observation belonging to each
% cluster: lb = sum_{i,k} E[z_ik] E[ln p(g(i) | mu_k,A_k)]

P  = size(m,1);
K  = size(m,2);
lb = 0;

for i=1:size(O,1) % For each combination of missing voxels

    % ---------------------------------------------------------------------
    % Get mask of missing values and modalities (with this particular code)
    io = O(i,:);                % Observed channels
    Po = sum(io);               % Number of observed channels
    if Po == 0, continue; end