getCodes( shaderStage ) {

		const codes = this.codes[ shaderStage ];

		let code = '';

		if ( codes !== undefined ) {

			for ( const nodeCode of codes ) {

				code += nodeCode.code + '\n';

			}

		}

		return code;

	}
Returns the native code definitions as a shader string for the given shader stage.

@param {('vertex'|'fragment'|'compute'|'any')} shaderStage - The shader stage.
@return {string} The native code section.