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_timelockanalysis.m
    path of file: ./repos/bspm/thirdparty/spm12/external/fieldtrip
    
    the code of the file until where you have to start completion: function [timelock] = ft_timelockanalysis(cfg, data)

% FT_TIMELOCKANALYSIS computes the timelocked average ERP/ERF and
% computes the covariance matrix
%
% Use as
%   [timelock] = ft_timelockanalysis(cfg, data)
%

    
function [timelock] = ft_timelockanalysis(cfg, data)

% FT_TIMELOCKANALYSIS computes the timelocked average ERP/ERF and
% computes the covariance matrix
%
% Use as
%   [timelock] = ft_timelockanalysis(cfg, data)
%
% The data should be organised in a structure as obtained from the
% FT_PREPROCESSING function. The configuration should be according to
%
%   cfg.channel            = Nx1 cell-array with selection of channels (default = 'all'),
%                            see FT_CHANNELSELECTION for details
%   cfg.trials             = 'all' or a selection given as a 1xN vector (default = 'all')
%   cfg.covariance         = 'no' or 'yes' (default = 'no')
%   cfg.covariancewindow   = 'prestim', 'poststim', 'all' or [begin end