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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def find_prekeyed(self, value, key):
 """ Find a value in a node, using a key function. The value is already a key. """


        while self is not NULL:
            direction = cmp(value, key(self.value))
            if direction < 0:
                self = self.left
            elif direction > 0:
                self = self.right
            elif direction == 0:
                return self.value