I have the code of a spherical gyroid written in Mathematica and I am unable to save it in STL format. The image is shown in the figure below and the code is shown below. I need help with a code on how to save it as an STL file.

[![enter image description here][1]][1]

 r = 2 Pi;
 model = ContourPlot3D[
 Sin[x] Cos[y] + Sin[y] Cos[z] + Sin[z] Cos[x] == 0, {x, -r, 
 r}, {y, -r, r}, {z, -r, r},
 RegionFunction -> ({x, y, z} \[Function] x^2 + y^2 + z^2 <= r^2),
 Mesh -> None, PlotTheme -> "ThickSurface", 
 Method -> {"Extrusion" -> .3}]


 [1]: https://i.sstatic.net/yxvMu.png