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

% Zero mean function. The mean function does not have any parameters.
%
% m(x) = 0
%

    
function [m,dm] = meanZero(hyp, x)

% Zero mean function. The mean function does not have any parameters.
%
% m(x) = 0
%
% Copyright (c) by Carl Edward Rasmussen and Hannes Nickisch, 2016-04-15.
%
% See also MEANFUNCTIONS.M.

if nargin<2, m = '0'; return; end