The LinkedSequenceAnimator interface.

  I created a linked-list class that implements the LinkedSequence and
  LinkedSequenceAnimator interfaces.  I was confused if I was supposed to
  implement the animator or just the sequence.

Your class should implement just the LinkedSequence interface.  The
LinkedSequenceAnimator interface should be used to declare an instance variable
to hold the instance passed in via the LinkedSequence.setAnimator() method.
Your code should use the instance variable to call the link() and unlink()
methods.

The assignment page has been updated to make this clear.