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: covGabor.m
    path of file: ./repos/Gaussian-Process-Regression/gpml-matlab-v4.2-2018-06-11/cov
    
    the code of the file until where you have to start completion: function [K,dK] = covGabor(mode, hyp, x, z)


    
function [K,dK] = covGabor(mode, hyp, x, z)

% Gabor covariance function with length scale ell and period p. The 
% covariance function is parameterized as:
%
% k(x,z) = h(x-z), h(t) = exp(-sum(t.^2./(2*ell.^2)))*cos(2*pi*sum(t./p)).
%
% The hyperparameters are:
%
% hyp = [ hyp_ell
%         hyp_p    ]
%
% We offer three different modes:
%   'eye':  ell =              ones(D,1);   p =            ones(D,1);
%   'iso':  ell = exp(hyp_ell)*ones(D,1);   p = exp(hyp_p)*ones(D,1);
%   'ard':  ell = exp(hyp_ell)          ;   p = exp(hyp_p)          ;
%
% Note that covSM implements a weighted sum of Gabor covariance functions, but
% using an alternative (spectral) parameterization.
%
% For more help on design of covariance functions, try "help covFunctions".
%
% Copyright (c) by Hannes Nickisch, 2016-05-03.
%
% See also COVFUNCTIONS.M, COVGABORARD.M, COVSM.M.

if nargin<1, error('We require a mode.'), end