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: fm_3dcs.m
    path of file: ./repos/3DCS/utils
    
    the code of the file until where you have to start completion: function [ y ] = fm_3dcs( A,x )
%FM_3DCS Forward model of three dimensional (3D) compressive sensing (CS).
%   y=FM_3DCS(A,x) returns the multiple frame vector of forward calculation
%   of CS, that is y_k=A_k*x_k for frame k, where A is the M-by-N-by-F 
%   sensing or measurement matrix, x is the N-by-F object matrix, and y is 
%   the M-by-F measurement matrix.

    
function [ y ] = fm_3dcs( A,x )
%FM_3DCS Forward model of three dimensional (3D) compressive sensing (CS).
%   y=FM_3DCS(A,x) returns the multiple frame vector of forward calculation
%   of CS, that is y_k=A_k*x_k for frame k, where A is the M-by-N-by-F 
%   sensing or measurement matrix, x is the N-by-F object matrix, and y is 
%   the M-by-F measurement matrix.
%   See also FMT_3DCS.
[M,N,F] = size(A);
for k = 1:F
    y(:,k) = A(:,:,k)*x(:,k);
end