class Node(object):
    
    '''A single node in a BST.  Contains references to left and right children,
    the parent, and a value.'''
    
    def __init__(self, value):
        '''Create a new node containing value.'''
        self.value = value
        self.left = None
        self.right = None
        self.parent = None
                  
    def splay(self):
        '''Perform a single splay step (at most two rotations).'''
        pass