/// <summary>
/// Adds the specified item at the beginning of the list.
/// </summary>
/// <param name="item"> The item to add. </param>
/// <returns> </returns>
public ImmList <T> AddFirst(T item)
{
var ret = Root.AddFirst(item, Lineage.Immutable).Wrap();
#if ASSERTS
ret.First.AssertEqual(item);
if (!IsEmpty)
{
ret.Last.AssertEqual(Last);
}
#endif
return(ret);
}