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: diffy.m
    path of file: ./repos/chebfun/@chebfun2v
    
    the code of the file until where you have to start completion: function G = diffy( F, n )
%DIFFY   Differentiate a CHEBFUN2V with respect to its first argument
%   DIFFY(F) returns a CHEBFUN2V representing the derivative of F in its first
%   argument. This is the same as DIFF(F,1,2).
%
%   DIFFY(F,N) returns a CHEBFUN2V representing the Nth derivative of F in its
%   first argument. This is the same as DIFF(F,N,2).
%

    
function G = diffy( F, n )
%DIFFY   Differentiate a CHEBFUN2V with respect to its first argument
%   DIFFY(F) returns a CHEBFUN2V representing the derivative of F in its first
%   argument. This is the same as DIFF(F,1,2).
%
%   DIFFY(F,N) returns a CHEBFUN2V representing the Nth derivative of F in its
%   first argument. This is the same as DIFF(F,N,2).
%
%   This command is for convenience as the syntax for DIFF, inherited from the
%   DIFF command for matrices, can be confusing.
% 
% See also DIFFX, DIFF. 

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

if ( nargin == 1 ) 
    % Default to first derivative. 
    n = 1; 
end