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: subsref.m
    path of file: ./repos/chebfun/@ballfunv
    
    the code of the file until where you have to start completion: function varargout = subsref(F, index)
%SUBSREF   BALLFUNV subsref.
%
% ( )
%   F(X,Y,Z) returns the values of the BALLFUNV F evaluated on the array 
%   (X,Y,Z) in cartesian coordinates. 
%
%   F(R, L, TH, 'spherical') returns the values of the BALLFUNV F evaluated
%   on the array (R,TH,LAM) in spherical coordinates. 
%
%   F(K) returns the first component of F if K = 1, the second if K = 2, and
%   the third if K = 3.
%
%   F(R, :, :, 'spherical') returns a SPHEREFUNV representing the BALLFUNV 

    
function varargout = subsref(F, index)
%SUBSREF   BALLFUNV subsref.
%
% ( )
%   F(X,Y,Z) returns the values of the BALLFUNV F evaluated on the array 
%   (X,Y,Z) in cartesian coordinates. 
%
%   F(R, L, TH, 'spherical') returns the values of the BALLFUNV F evaluated
%   on the array (R,TH,LAM) in spherical coordinates. 
%
%   F(K) returns the first component of F if K = 1, the second if K = 2, and
%   the third if K = 3.
%
%   F(R, :, :, 'spherical') returns a SPHEREFUNV representing the BALLFUNV 
%   F along a radial shell. 
%
%   F(:, :, :) returns F.
%
%  .
%   F.PROP returns the property PROP of F as defined by GET(F,'PROP').
%
% { }
%    Throws an error.

% Copyright 2019 by The University of Oxford and The Chebfun Developers.
% See http://www.chebfun.org/ for Chebfun information.

% check for empty CHEBFUN2V object.
if ( isempty(F) )
    varargout = {[]};
    return
end