Unwrapping.GenerateSecondaryUVSet save auto ?

Ok I got an answer if some people are interesting to do this :

 //Recursive function switch all uv2 of mesh to true
     private void GenerateLightMapUV2( GameObject gameObject )
     {
         MeshFilter meshFilter = gameObject.GetComponent<MeshFilter>();
         MeshRenderer meshRenderer = gameObject.GetComponent<MeshRenderer>();
 
         //Check if my mesh have and filter and a renderer so it's the final
         if( meshFilter != null && meshRenderer != null )
         {
             //Take the mesh of the file
             Mesh meshLightmapped = meshFilter.sharedMesh;
 
             //Take the file's path and put it in a string
             string path = AssetDatabase.GetAssetPath( meshLightmapped );
             //Define a modelImporter to modify its importing settings
             ModelImporter model = AssetImporter.GetAtPath( path ) as ModelImporter;
 
             //Put the generateSecondaryUV field to true and GenerateUVSet for the mesh
             model.generateSecondaryUV = true;
             Unwrapping.GenerateSecondaryUVSet( meshLightmapped );
 
             //Update the mesh setting in editor
             AssetDatabase.ImportAsset( path );
         }
             //If the previous mesh don't have both so go in children
         foreach( Transform t in gameObject.transform )
             GenerateLightMapUV2( t.gameObject );
     }