To make this LinkedList a little more interesting, we will develop a contains method similar to the one that we developed for the BST:

static func contains(_ key: Element, list: LinkedList<Element>) -> Bool { 
     switch list { 
     case .end: 
         return false 
     case .node(let data, let next): 
         if key == data { 
             return true 
         } else { 
             return contains(key, list: next) 
         } 
     } 
} 

This method recursively checks for a specific element in LinkedList and returns true if it finds the element:

print(LinkedList.contains(1, list: functionalLinkedList)) 

The result of this expression is going to be true.