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: covSEiso.m
    path of file: ./repos/hctsa/Toolboxes/gpml/cov
    
    the code of the file until where you have to start completion: function K = covSEiso(hyp, x, z, i)

% Squared Exponential covariance function with isotropic distance measure. The
% covariance function is parameterized as:
%
% k(x^p,x^q) = sf^2 * exp(-(x^p - x^q)'*inv(P)*(x^p - x^q)/2) 
%

    
function K = covSEiso(hyp, x, z, i)

% Squared Exponential covariance function with isotropic distance measure. The
% covariance function is parameterized as:
%
% k(x^p,x^q) = sf^2 * exp(-(x^p - x^q)'*inv(P)*(x^p - x^q)/2) 
%
% where the P matrix is ell^2 times the unit matrix and sf^2 is the signal
% variance. The hyperparameters are:
%
% hyp = [ log(ell)
%         log(sf)  ]
%
% For more help on design of covariance functions, try "help covFunctions".
%
% Copyright (c) by Carl Edward Rasmussen and Hannes Nickisch, 2010-09-10.
%
% See also COVFUNCTIONS.M.

if nargin<2, K = '2'; return; end