how to write a trained fuzzy FIS tree to disk

Hi all!

I can't write the tree of trained fuzzy inference systems to disk. At the bottom of the program are the options that I used. But they don't work...

 Granulator = mamfis('Name','Granulator','NumInputs',2,'NumOutputs',1);
    Granulator.Inputs(1).Name = "G_inp1"; 
    Granulator.Inputs(2).Name = "G_inp2"; 
    Granulator.Outputs(1).Name = "G_out";
    
    CTMCM = mamfis('Name','CTMCM','NumInputs',2,'NumOutputs',1);
    CTMCM.Inputs(1).Name = "CTMCM_inp1"; 
    CTMCM.Inputs(2).Name = "CTMCM_inp2"; 
    CTMCM.Outputs(1).Name = "CTMCM_out";
        
    OTF = mamfis('Name','OTF','NumInputs',2,'NumOutputs',1);
    OTF.Inputs(1).Name = "OTF_inp1"; 
    OTF.Inputs(2).Name = "OTF_inp2"; 
    OTF.Outputs(1).Name = "OTF_out";
    con1 = ["Granulator/G_out" "CTMCM/CTMCM_inp1"];
    con2 = ["CTMCM/CTMCM_out" "OTF/OTF_inp1"];
    tree = fistree([Granulator CTMCM OTF],[con1;con2]);
    plotfis(tree)      % FIS tree structure
X=rand(1000,5);        % imitation of original data
nn=size(X);
nt=round(0.8*nn(1,1)); % training sample size
trnX = X(1:nt,1:4);
trnY = X(1:nt,end);
vldX = X(nt+1:end,1:4);
vldY = X(nt+1:end,end);
options = tunefisOptions;
options.Method = 'particleswarm';
options.OptimizationType = 'learning';
options.NumMaxRules = 10;
options.UseParallel = false; 
options.MethodOptions.MaxIterations = 2;
rng('default')
fisout1 = tunefis(tree,[],trnX,trnY,options);
% writeFIS(fisout1,'fis1') % does not work
% writeFIS(tree,'fis1')    % does not work