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: kr.m
    path of file: ./repos/imtsl/libs/tensorlab
    
    the code of the file until where you have to start completion: function X = kr(U,varargin)
%KR Khatri-Rao product.
%   kr(A,B) returns the Khatri-Rao product of two matrices A and B, of 
%   dimensions I-by-K and J-by-K respectively. The result is an I*J-by-K
%   matrix formed by the matching columnwise Kronecker products, i.e.,
%   the k-th column of the Khatri-Rao product is defined as
%   kron(A(:,k),B(:,k)).
%
%   kr(A,B,C,...) and kr({A B C ...}) compute a string of Khatri-Rao 
%   products A x B x C x ..., where x denotes the Khatri-Rao product.

    
function X = kr(U,varargin)
%KR Khatri-Rao product.
%   kr(A,B) returns the Khatri-Rao product of two matrices A and B, of 
%   dimensions I-by-K and J-by-K respectively. The result is an I*J-by-K
%   matrix formed by the matching columnwise Kronecker products, i.e.,
%   the k-th column of the Khatri-Rao product is defined as
%   kron(A(:,k),B(:,k)).
%
%   kr(A,B,C,...) and kr({A B C ...}) compute a string of Khatri-Rao 
%   products A x B x C x ..., where x denotes the Khatri-Rao product.
%
%   See also kron.

%   Authors: Laurent Sorber (Laurent.Sorber@cs.kuleuven.be)
%            Marc Van Barel (Marc.VanBarel@cs.kuleuven.be)
%            Lieven De Lathauwer (Lieven.DeLathauwer@kuleuven-kulak.be)

if ~iscell(U), U = [{U} varargin]; end