UnityEditor.ShaderUtil.GetShaderVariantEntries C# (CSharp) Method

        internal static extern void GetShaderVariantEntries(Shader shader, ShaderVariantCollection skipAlreadyInCollection, out int[] types, out string[] keywords);
        /// <summary>

 private void DisplayAddVariantsWindow(Shader shader, ShaderVariantCollection collection)
 {
     AddShaderVariantWindow.PopupData popupData = new AddShaderVariantWindow.PopupData();
     popupData.shader     = shader;
     popupData.collection = collection;
     string[] array;
     ShaderUtil.GetShaderVariantEntries(shader, collection, out popupData.types, out array);
     if (array.Length == 0)
     {
         EditorApplication.Beep();
     }
     else
     {
         popupData.keywords = new string[array.Length][];
         for (int i = 0; i < array.Length; i++)
         {
             popupData.keywords[i] = array[i].Split(new char[]
             {
                 ' '
             });
         }
         AddShaderVariantWindow.ShowAddVariantWindow(popupData);
         GUIUtility.ExitGUI();
     }
 }