src/vs/workbench/common/editor/sideBySideEditorInput.ts/AbstractSideBySideEditorInputSerializer/getInputSerializers
class AbstractSideBySideEditorInputSerializer:	private getInputSerializers(secondaryEditorInputTypeId: string, primaryEditorInputTypeId: string): [IEditorInputSerializer | undefined, IEditorInputSerializer | undefined] {
		const registry = Registry.as<IEditorInputFactoryRegistry>(EditorExtensions.EditorInputFactories);

		return [registry.getEditorInputSerializer(secondaryEditorInputTypeId), registry.getEditorInputSerializer(primaryEditorInputTypeId)];
	}