private void AddSpriteSheet(IExportContainer container, TextureImporter importer)
 {
     if (importer.SpriteMode == SpriteImportMode.Single)
     {
         var            kvp   = m_sprites.First();
         SpriteMetaData smeta = kvp.Key.GenerateSpriteMetaData(container, kvp.Value);
         importer.SpriteSheet = new SpriteSheetMetaData(ref smeta);
     }
     else
     {
         List <SpriteMetaData> metadata = new List <SpriteMetaData>(m_sprites.Count);
         foreach (var kvp in m_sprites)
         {
             SpriteMetaData smeta = kvp.Key.GenerateSpriteMetaData(container, kvp.Value);
             if (SpriteMetaData.HasInternalID(container.ExportVersion))
             {
                 smeta.InternalID = ObjectUtils.GenerateInternalID();
             }
             metadata.Add(smeta);
         }
         importer.SpriteSheet.Sprites = metadata.ToArray();
     }
 }