def to_a
      current = @first
      array = []
      while !current.nil?
        array << current.data
        current = current.next
      end
      array
    end
def to_a
      current = @first
      array = []
      while !current.nil?
        array << current.data
        current = current.next
      end
      array
    end
Returns an array containing the data from the nodes in the list