static get type() {

		return 'FunctionNode';

	}
This class represents a native shader function. It can be used to implement
certain aspects of a node material with native shader code. There are two predefined
TSL functions for easier usage.

- `wgslFn`: Creates a WGSL function node.
- `glslFn`: Creates a GLSL function node.

A basic example with one include looks like so:

```js
const desaturateWGSLFn = wgslFn( `
	fn desaturate( color:vec3<f32> ) -> vec3<f32> {
		let lum = vec3<f32>( 0.299, 0.587, 0.114 );
		return vec3<f32>( dot( lum, color ) );
	}`
);
const someWGSLFn = wgslFn( `
	fn someFn( color:vec3<f32> ) -> vec3<f32> {
		return desaturate( color );
	}
`, [ desaturateWGSLFn ] );
material.colorNode = someWGSLFn( { color: texture( map ) } );
```
@augments CodeNode