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: mne_pick_channels_cov.m
    path of file: ./repos/malini/Codes/deconvolution - model/spm8/external/mne
    
    the code of the file until where you have to start completion: function [cov] = mne_pick_channels_cov(orig,include,exclude)
%
% [cov] = mne_pick_channels_cov(orig,include,exclude)
%
% Pick desired channels from a covariance matrix
%
% orig      - The original covariance matrix
% include   - Channels to include (if empty, include all available)
% exclude   - Channels to exclude (if empty, do not exclude any)
%
%

    
function [cov] = mne_pick_channels_cov(orig,include,exclude)
%
% [cov] = mne_pick_channels_cov(orig,include,exclude)
%
% Pick desired channels from a covariance matrix
%
% orig      - The original covariance matrix
% include   - Channels to include (if empty, include all available)
% exclude   - Channels to exclude (if empty, do not exclude any)
%
%

%
%
%   Author : Matti Hamalainen, MGH Martinos Center
%   License : BSD 3-clause
%
%   Revision 1.9  2006/11/21 12:53:49  msh
%   Fixed error in picking
%
%   Revision 1.8  2006/06/29 22:12:28  msh
%   Fixed errors in channel picking
%
%   Revision 1.7  2006/05/03 18:53:05  msh
%   Approaching Matlab 6.5 backward compatibility
%
%   Revision 1.6  2006/04/23 15:29:40  msh
%   Added MGH to the copyright
%
%   Revision 1.5  2006/04/18 20:44:46  msh
%   Added reading of forward solution.
%   Use length instead of size when appropriate
%
%   Revision 1.4  2006/04/15 12:21:00  msh
%   Several small improvements
%
%   Revision 1.3  2006/04/14 15:49:49  msh
%   Improved the channel selection code and added ch_names to measurement info.
%
%   Revision 1.2  2006/04/14 00:45:42  msh
%   Added channel picking and fiff_invert_transform
%
%   Revision 1.1  2006/04/13 17:05:45  msh
%   Added reading of bad channels to fiff_read_meas_info.m
%   Added mne_pick_channels_cov.m
%
%

me='MNE:mne_pick_channels_cov';

if nargin == 1
    cov = orig;
    if isempty(cov.eig) || isempty(cov.eigvec)
        decompose_eigen; 
    end