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: ktFOCUSS4D.m
    path of file: ./repos/CS_MoCo_LAB/reconstruction/matlab/CS_LAB_matlab/@FOCUSS
    
    the code of the file until where you have to start completion: function dImg = ktFOCUSS4D(obj, kSpace)
% 4D FOCUSS algorithm
%
% input:
% obj       CS reconstruction object (holding all parameters)
% kSpace    subsampled kSpace
%
% output:
% dImg      reconstructed channel individual image
%
% (c) Thomas Kuestner 
% ---------------------------------------------------------------------

% here: kSpace: k_y - k_z - k_x - cha - t
% calibSize: k_y - k_x - k_z (cell: t)

    
function dImg = ktFOCUSS4D(obj, kSpace)
% 4D FOCUSS algorithm
%
% input:
% obj       CS reconstruction object (holding all parameters)
% kSpace    subsampled kSpace
%
% output:
% dImg      reconstructed channel individual image
%
% (c) Thomas Kuestner 
% ---------------------------------------------------------------------

% here: kSpace: k_y - k_z - k_x - cha - t
% calibSize: k_y - k_x - k_z (cell: t)
% fft: f -> t   x -> k_x   y -> k_y

fprintf(' |- prepare k-space and image kernel...\n');
evalin('caller', 'clear ''kSpaceL'';');
[nTime, nPha, nZ, nFreq, nCha] = size(kSpace);

% retrieve mask
obj.fullMask = permute(obj.fullMask, [5 1 2 3 4]); % t-k_y-k_z-k_x/x-cha

% prepare initial estimate
fprintf(' |- prepare initial estimate...\n');
W = kSpace; % t-k_y-k_z-x-cha
helper = true(size(W));
m = [nPha, nZ, nFreq, nCha];
if(iscell(obj.calibSize))
    % automatically determined calibration size
    loop = nTime;
    pos = 't,idx{1},idx{2},idx{3},:';
else
    % predefined calibration size
    loop = 1;
    pos = ':,idx{1},idx{2},idx{3},:';
end