namespace System.Collections.Generic;
/// Items that can be added and taken away.
[Intrinsic]
public interface ICollection<T> : IEnumerable<T> {
i32 Count { get; }
bool IsReadOnly { get; }
void Add(T item);
void Clear();
readonly bool Contains(T item);
/// Whether `item` was there to take away.
bool Remove(T item);
}