Problem 2.1: Remove Duplicates (100 pts)

Write a function that takes a sorted linked list of integers and mutates it so that all duplicates are removed.

Your implementation should mutate the original linked list. Do not create any new linked lists.

def remove_duplicates(lnk):
    """ Remove all duplicates in a sorted linked list.

    >>> lnk = Link(1, Link(1, Link(1, Link(1, Link(5)))))
    >>> Link.__init__, hold = lambda *args: print("Do not steal chicken!"), Link.__init__
    >>> try:
    ...     remove_duplicates(lnk)
    ... finally:
    ...     Link.__init__ = hold
    >>> lnk
    Link(1, Link(5))
    """
    "*** YOUR CODE HERE ***"