AssetLoaderToken Instances of this class are returned as tokens by loading operations to provide an object on which events can be listened for in cases where the actual asset loader is not directly available (e.g.
 ResourceDependency ResourceDependency represents the data required to load, parse and resolve additional files ("dependencies") required by a parser, used by ResourceLoadSession.
 SingleFileLoader The SingleFileLoader is used to load a single file, as part of a resource.