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

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