def push *elements
      elements.each do |element|
        node = LLNode.new(element, nil, @last)
        @first = node if @first.nil?
        @last.next = node unless @last.nil?
        @last = node
        @size += 1
      end
      self
    end
def push *elements
      elements.each do |element|
        node = LLNode.new(element, nil, @last)
        @first = node if @first.nil?
        @last.next = node unless @last.nil?
        @last = node
        @size += 1
      end
      self
    end
Append - Pushes the given object(s) on to the end of this
 Linked List. The expression returns the list itself, so several
 appends may be chained together. See also #pop for the opposite effect.