diff --git a/packages/core/src/common/unit.ts b/packages/core/src/common/unit.ts
index 4949259b4fe..c817d6baa91 100644
--- a/packages/core/src/common/unit.ts
+++ b/packages/core/src/common/unit.ts
@@ -29,23 +29,3 @@ export abstract class UnitModel<_D = object, T extends UnitType = UnitType> exte
     abstract name$: Observable<string>;
     abstract setName(name: string): void;
 }
-
-interface IMixinProperty<T> {
-    // eslint-disable-next-line ts/no-explicit-any
-    [fnName: string]: (this: T, ...args: any[]) => any;
-}
-
-/**
- * Mixin some methods to targetObject as prototype, the static methods will not be mixed in
- * @param {T} targetClass The target class to mixin
- * @param {IMixinProperty<T>} mixin The mixin object which contains the methods to mixin.
- */
-export function mixinClass<T>(targetClass: T, mixin: IMixinProperty<T>): void {
-    for (const key in mixin) {
-        // eslint-disable-next-line no-prototype-builtins
-        if (mixin.hasOwnProperty(key)) {
-            // @ts-ignore
-            targetClass.prototype[key] = mixin[key];
-        }
-    }
-}
diff --git a/packages/facade/src/apis/sheets/f-workbook.ts b/packages/facade/src/apis/sheets/f-workbook.ts
index 99e9adf8259..a7956638a84 100644
--- a/packages/facade/src/apis/sheets/f-workbook.ts
+++ b/packages/facade/src/apis/sheets/f-workbook.ts
@@ -41,7 +41,7 @@ export class FWorkbook {
 
     constructor(
         private readonly _workbook: Workbook,
-        @Inject(Injector) protected readonly _injector: Injector,
+        @Inject(Injector) private readonly _injector: Injector,
         @Inject(IResourceLoaderService) private readonly _resourceLoaderService: IResourceLoaderService,
         @Inject(SheetsSelectionsService) private readonly _selectionManagerService: SheetsSelectionsService,
         @IUniverInstanceService private readonly _univerInstanceService: IUniverInstanceService,