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: ft_headmodel_localspheres.m
    path of file: ./repos/fieldtrip/forward
    
    the code of the file until where you have to start completion: function headmodel = ft_headmodel_localspheres(mesh, grad, varargin)

% FT_HEADMODEL_LOCALSPHERES constructs a MEG volume conduction model in
% with a local sphere fitted to the head or brain surface for each separate
% channel
%
% This implements
%   Huang MX, Mosher JC, Leahy RM. "A sensor-weighted overlapping-sphere
%   head model and exhaustive head model comparison for MEG." Phys Med
%   Biol. 1999 Feb;44(2):423-40
%
% Use as
%   headmodel = ft_headmodel_localspheres(mesh, grad, ...)
%
% Optional arguments should be specified in key-value pairs and can include
%   radius    = number, radius of sphere within which headshape points will
%               be included for the fitting algorithm

    
function headmodel = ft_headmodel_localspheres(mesh, grad, varargin)

% FT_HEADMODEL_LOCALSPHERES constructs a MEG volume conduction model in
% with a local sphere fitted to the head or brain surface for each separate
% channel
%
% This implements
%   Huang MX, Mosher JC, Leahy RM. "A sensor-weighted overlapping-sphere
%   head model and exhaustive head model comparison for MEG." Phys Med
%   Biol. 1999 Feb;44(2):423-40
%
% Use as
%   headmodel = ft_headmodel_localspheres(mesh, grad, ...)
%
% Optional arguments should be specified in key-value pairs and can include
%   radius    = number, radius of sphere within which headshape points will
%               be included for the fitting algorithm
%   maxradius = number, if for a given sensor the fitted radius exceeds
%               this value, the radius and origin will be replaced with the
%               single sphere fit
%   baseline  = number
%   feedback  = boolean, true or false
%
% See also FT_PREPARE_HEADMODEL, FT_PREPARE_VOL_SENS, FT_COMPUTE_LEADFIELD

% Copyright (C) 2012, Donders Centre for Cognitive Neuroimaging, Nijmegen, NL
%
% This file is part of FieldTrip, see http://www.fieldtriptoolbox.org
% for the documentation and details.
%
%    FieldTrip is free software: you can redistribute it and/or modify
%    it under the terms of the GNU General Public License as published by
%    the Free Software Foundation, either version 3 of the License, or
%    (at your option) any later version.
%
%    FieldTrip is distributed in the hope that it will be useful,
%    but WITHOUT ANY WARRANTY; without even the implied warranty of
%    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
%    GNU General Public License for more details.
%
%    You should have received a copy of the GNU General Public License
%    along with FieldTrip. If not, see <http://www.gnu.org/licenses/>.
%
% $Id$

% get the additional inputs and set the defaults
feedback      = ft_getopt(varargin, 'feedback', true);
singlesphere  = ft_getopt(varargin, 'singlesphere', 'no');

if any(strcmp(varargin(1:2:end