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_read_sens.m
    path of file: ./repos/malini/Codes/deconvolution - model/spm8/external/fieldtrip/fileio
    
    the code of the file until where you have to start completion: function [sens] = ft_read_sens(filename, varargin)

% FT_READ_SENS read sensor positions from various manufacturer
% specific files. The following acsuisition system and analysis
% platform EEG and MEG file formats are currently supported:
%
%   asa_elc besa_elp besa_pos besa_sfp yokogawa_ave yokogawa_con
%   yokogawa_raw 4d 4d_pdf 4d_m4d 4d_xyz ctf_ds ctf_res4 itab_raw
%   itab_mhd netmeg neuromag_fif neuromag_mne neuromag_mne_elec
%   neuromag_mne_grad polhemus_fil polhemus_pos zebris_sfp spmeeg_mat
%   eeglab_set matlab
%
% Use as
%   grad = ft_read_sens(filename, ...)  % for gradiometers
%   elec = ft_read_sens(filename, ...)  % for electrodes
%
% Additional options should be specified in key-value pairs and can be
%   'fileformat' = string, see the list of supported file formats (the
%                  default is determined automatically)
%
% An electrode definition contain the following fields
%   elec.elecpos = Nx3 matrix with carthesian (x,y,z) coordinates of each
%                  electrode
%   elec.label   = cell-array of length N with the label of each electrode
%   elec.chanpos = Nx3 matrix with coordinates of each sensor
%
% A gradiometer definition generally consists of multiple coils per
% channel, e.g.two coils for a 1st order gradiometer in which the
% orientation of the coils is opposite. Each coil is described
% separately and a large "tra" matrix has to be given that defines
% how the forward computed field is combined over the coils to generate
% the output of each channel. The gradiometer definition constsis of
% the following fields
%   grad.coilpos = Mx3 matrix with the position of each coil
%   grad.coilori = Mx3 matrix with the orientation of each coil
%   grad.tra     = NxM matrix with the weight of each coil into each channel
%   grad.label   = cell-array of length N with the label of each of the channels
%   grad.chanpos = Nx3 matrix with the positions of each sensor
%
% See also FT_TRANSFORM_SENS, FT_PREPARE_VOL_SENS, FT_COMPUTE_LEADFIELD,

    
function [sens] = ft_read_sens(filename, varargin)

% FT_READ_SENS read sensor positions from various manufacturer
% specific files. The following acsuisition system and analysis
% platform EEG and MEG file formats are currently supported:
%
%   asa_elc besa_elp besa_pos besa_sfp yokogawa_ave yokogawa_con
%   yokogawa_raw 4d 4d_pdf 4d_m4d 4d_xyz ctf_ds ctf_res4 itab_raw
%   itab_mhd netmeg neuromag_fif neuromag_mne neuromag_mne_elec
%   neuromag_mne_grad polhemus_fil polhemus_pos zebris_sfp spmeeg_mat
%   eeglab_set matlab
%
% Use as
%   grad = ft_read_sens(filename, ...)  % for gradiometers
%   elec = ft_read_sens(filename, ...)  % for electrodes
%
% Additional options should be specified in key-value pairs and can be
%   'fileformat' = string, see the list of supported file formats (the
%                  default is determined automatically)
%
% An electrode definition contain the following fields
%   elec.elecpos = Nx3 matrix with carthesian (x,y,z) coordinates of each
%                  electrode
%   elec.label   = cell-array of length N with the label of each electrode
%   elec.chanpos = Nx3 matrix with coordinates of each sensor
%
% A gradiometer definition generally consists of multiple coils per
% channel, e.g.two coils for a 1st order gradiometer in which the
% orientation of the coils is opposite. Each coil is described
% separately and a large "tra" matrix has to be given that defines
% how the forward computed field is combined over the coils to generate
% the output of each channel. The gradiometer definition constsis of
% the following fields
%   grad.coilpos = Mx3 matrix with the position of each coil
%   grad.coilori = Mx3 matrix with the orientation of each coil
%   grad.tra     = NxM matrix with the weight of each coil into each channel
%   grad.label   = cell-array of length N with the label of each of the channels
%   grad.chanpos = Nx3 matrix with the positions of each sensor
%
% See also FT_TRANSFORM_SENS, FT_PREPARE_VOL_SENS, FT_COMPUTE_LEADFIELD,
% FT_DATATYPE_SENS

% Copyright (C) 2005-2010 Robert Oostenveld
%
% This file is part of FieldTrip, see http://www.ru.nl/neuroimaging/fieldtrip
% 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: ft_read_sens.m 7369 2013-01-21 14:14:11Z vlalit $

% optionally get the data from the URL and make a temporary local copy
filename = fetch_url(filename);

% test whether the file exists
if ~exist(filename, 'file')
  error('file ''%s'' does not exist', filename);
end