Expected an assignment or function call and instead saw an expression no-unused-expressions with react

I am developing a website using my opinion. This error appears and I do not know how to solve it

 Expected an assignment or function call and instead saw an expression  no-unused-expressions

it is appears in extraReducers section

my code :

const bookSlice = createSlice({
  name: 'book',
  initialState: { books: [], isLoading: false, error: null, book: null },
  reducers: {},
  extraReducers: (builder) => {
    //GET BOOKS
      builder.addCase(getBooks.pending, (state) => {
      state.isLoading = true;
      state.error = null;
    }),
      builder.addCase(getBooks.fulfilled, (state, action) => {
        state.isLoading = false;
        state.books = action.payload;
      }),
      builder.addCase(getBooks.rejected, (state, action) => {
        state.isLoading = false;
        state.error = action.payload;
      }),
      // INSERT BOOK
      builder.addCase(insertBook.pending, (state) => {
        state.isLoading = true;
        state.error = null;
      }),
      builder.addCase(insertBook.fulfilled, (state, action) => {
        state.isLoading = false;
        state.books.push(action.payload);
      }),
      builder.addCase(insertBook.rejected, (state, action) => {
        state.isLoading = false;
        state.error = action.payload;
      });
  },
});

how to solve that error ?