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: FFT3D.m
    path of file: ./repos/CS_MoCo_LAB/reconstruction/matlab/CS_LAB_matlab/utils/utils_Proximal
    
    the code of the file until where you have to start completion: function [ y ] = FFT3D( x )
%FFT3D Summary of this function goes here

    
function [ y ] = FFT3D( x )
%FFT3D Summary of this function goes here
%   Detailed explanation goes here

y = fftshift(fftn(ifftshift(x)));

end