public interface IMenu { void Add(string item); void Remove(string item); void Display(); }In the above example, we define the IMenu interface with three methods: Add, Remove, and Display. The Add method takes a string as input and adds it to the menu, the Remove method takes a string as input and removes it from the menu, and the Display method displays the menu. One package library that includes the IMenu interface is the System.Windows.Forms namespace in the .NET Framework. This namespace contains classes for creating Windows-based applications, including various user interface controls such as menus. Developers can use this namespace to create menus that implement the IMenu interface and customize them to fit their application's needs.