Optionalgetused for making a cache key to check for reusability, currently only used for webgl ShaderTypes but might be needed for other types of renderer
OptionalpropsValues you use to draw the Shader
Optionaltimetimer that updates every loop, by default uses the stage elapsed time If you want to do a special calculation you can define a function. When you calculate your own value you can use the Stage timing values deltaTime, lastFrameTime, and currentFrameTime;
CoreShaderType is a template for ShaderTypes the renderer. You could view a ShaderType as a configuration object that contains methods, and values that you can use to alter the way a node is drawn by the Renderer.