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This problem was asked by Google.

Given an iterator with methods next() and hasNext(), create a wrapper iterator, PeekableInterface, which also implements peek(). peek shows the next element that would be returned on next().

Here is the interface:

class PeekableInterface(object):
    def __init__(self, iterator):
        pass

    def peek(self):
        pass

    def next(self):
        pass

    def hasNext(self):
        pass