/// <summary>
 /// Searches local collection to find all Book objects that contain the searchtoken
 /// </summary>
 /// <param name="searchToken">string used to find Books in collection</param>
 /// <returns>BookInventory that contains all Book objects that contain searchToken</returns>
 public BookInventory SearchBookInventory(string searchToken)
 {
     return(bookInventory.FindAll(searchToken));
 }