A custom visual shader graph expression written in Godot Shading Language. Custom Godot Shading Language expression, with a custom amount of input and output ports. The provided code is directly injected into the graph's matching shader function ([code]vertex[/code], [code]fragment[/code], or [code]light[/code]), so it cannot be used to declare functions, varyings, uniforms, or global constants. See [VisualShaderNodeGlobalExpression] for such global definitions. An expression in Godot Shading Language, which will be injected at the start of the graph's matching shader function ([code]vertex[/code], [code]fragment[/code], or [code]light[/code]), and thus cannot be used to declare functions, varyings, uniforms, or global constants.