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: jacobian.m
    path of file: ./repos/chebfun/@diskfunv
    
    the code of the file until where you have to start completion: function J = jacobian( F )
%JACOBIAN   Jacobian determinant of a DISKFUNV.
%   J = JACOBIAN(F) computes the determinant of the Jacobian matrix associated
%   with the vector-valued DISKFUNV F. 
%
%   Note we return the determinant of the Jacobian matrix and not the Jacobian
%   matrix itself.
%
% See also DISKFUN/GRADIENT. 


    
function J = jacobian( F )
%JACOBIAN   Jacobian determinant of a DISKFUNV.
%   J = JACOBIAN(F) computes the determinant of the Jacobian matrix associated
%   with the vector-valued DISKFUNV F. 
%
%   Note we return the determinant of the Jacobian matrix and not the Jacobian
%   matrix itself.
%
% See also DISKFUN/GRADIENT. 

% Copyright 2017 by The University of Oxford and The Chebfun Developers.
% See http://www.chebfun.org/ for Chebfun information.

% Empty check: 
if ( isempty( F ) )  
    J = diskfun; 
    return 
end