/// <summary>
/// Determines whether an element is in the <see cref="BlockStack{T}"/>
/// </summary>
/// <param name="item">
/// The object to locate in the System.Collections.Generic.Stack`1. The value can
/// be null for reference types.
/// </param>
/// <returns></returns>
public bool Contains(T item) => Header.Contains(item) ? true : Elements.Contains(item) ? true : Footer.Contains(item) ? true & UseSeparator : Separator.Equals(item) ? true : false;