jellyfin-server/MediaBrowser.Controller/Resolvers/TV/EpisodeResolver.cs

using MediaBrowser.Controller.Entities.TV;
using MediaBrowser.Controller.Library;
using System.ComponentModel.Composition;

namespace MediaBrowser.Controller.Resolvers.TV
{
    [Export(typeof(IBaseItemResolver))]
    public class EpisodeResolver : BaseVideoResolver<Episode>
    {
        protected override Episode Resolve(ItemResolveEventArgs args)
        {
            // If the parent is a Season or Series, then this is an Episode if the VideoResolver returns something
            if (args.Parent is Season || args.Parent is Series)
            {
                return base.Resolve(args);
            }

            return null;
        }
    }
}