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_infinite.m
    path of file: ./repos/bspm/thirdparty/spm12/external/fieldtrip/forward
    
    the code of the file until where you have to start completion: function headmodel = ft_headmodel_infinite(varargin)

% FT_HEADMODEL_INFINITE returns an infinitely large homogenous
% volume conduction model. For EEG the volume conductor can be used
% to compute the leadfield of electric current dipoles, for MEG it
% can be used for computing the leadfield of magnmetic dipoles.
%
% Use as
%   headmodel = ft_headmodel_infinite;
%
% See also 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/>.
%
% $Id$

sourcemodel = ft_getopt(varargin, 'sourcemodel', 'default');

% this is an easy one
headmodel = [];

switch sourcemodel
  case 'monopole'
    headmodel.type = 'infinite_monopole';
  case 'magneticdipole'
    headmodel.type = 'infinite_magneticdipole';
  case 'currentdipole'
    headmodel.type = 'infinite_currentdipole';

    
function headmodel = ft_headmodel_infinite(varargin)

% FT_HEADMODEL_INFINITE returns an infinitely large homogenous
% volume conduction model. For EEG the volume conductor can be used
% to compute the leadfield of electric current dipoles, for MEG it
% can be used for computing the leadfield of magnmetic dipoles.
%
% Use as
%   headmodel = ft_headmodel_infinite;
%
% See also 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/>.
%
% $Id$

sourcemodel = ft_getopt(varargin, 'sourcemodel', 'default');

% this is an easy one
headmodel = [];

switch sourcemodel
  case 'monopole'
    headmodel.type = 'infinite_monopole';
  case 'magneticdipole'
    headmodel.type = 'infinite_magneticdipole';
  case 'currentdipole'
    headmodel.type = 'infinite_currentdipole';
  case 'default'
    % let the EEG or MEG leadfield code decide
    headmodel.type = 'infinite';
end