.stl file generation with multiple tetrahedron inside cube

i used command stlwrite but got the error

"Error using stlwrite (line 33)

Tetrahedron triangulation is not supported. "

i m trying to use this function but dont understand mistake or concept .

https://ww2.mathworks.cn/matlabcentral/fileexchange/20922-stlwrite-write-ascii-or-binary-stl-files

https://ww2.mathworks.cn/matlabcentral/fileexchange/24400-stl_export..

the variable has been uploaded .using 2nd function of stl export i get only triangle not tetra hedrons

e.g

i=1;

a=A{i};

DT3 = delaunayTriangulation(a);

nodes_file =DT3.Points ;

triangles_file=DT3.ConnectivityList ;

STL_file_name='abc.stl';

solid='defg';

[normalized_normal_vectors]=STL_Export(nodes_file, triangles_file, STL_file_name,solid);.

how to make the .stl file of tetrahedron ?

the resutls i get ..not tetrahedron but only triangles ?