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: bf_inverse_eloreta.m
    path of file: ./repos/spm12/toolbox/DAiSS
    
    the code of the file until where you have to start completion: function res = bf_inverse_eloreta(BF, S)

    
function res = bf_inverse_eloreta(BF, S)
% Computes eLORETA projectors
% Copyright (C) 2013 Wellcome Trust Centre for Neuroimaging

% Vladimir Litvak, using the code from Guido Nolte
%
% please cite
% R.D. Pascual-Marqui: Discrete, 3D distributed, linear imaging methods of electric neuronal activity. Part 1: exact, zero
% error localization. arXiv:0710.3341 [math-ph], 2007-October-17, http://arxiv.org/pdf/0710.3341

% $Id: bf_inverse_eloreta.m 7706 2019-11-22 16:30:29Z spm $

%--------------------------------------------------------------------------
if nargin == 0
    regularisation = cfg_entry;
    regularisation.tag = 'regularisation';
    regularisation.name = 'Regularisation parameter';
    regularisation.strtype = 'r';
    regularisation.num = [1 1];
    regularisation.val = {0.05};
    regularisation.help = {'Optional regularization parameter (default is .05 corresponding ',...
        'to 5% of the average of the eigenvalues of some matrix to be inverted.)'};
    
    
    eloreta      = cfg_branch;
    eloreta.tag  = 'eloreta';
    eloreta.name = 'eLORETA';
    eloreta.val  = {regularisation};
    eloreta.help = {'eLORETA implementation by Guido Nolte',...
        'Please cite',...
        'R.D. Pascual-Marqui: Discrete, 3D distributed, linear imaging methods of electric neuronal activity. Part 1: exact, zero',...
        'error localization. arXiv:0710.3341 [math-ph], 2007-October-17, http://arxiv.org/pdf/0710.3341'};
    
    res = eloreta;
    
    return
elseif nargin < 2
    error('Two input arguments are required');
end