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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 next_sibling(self):
 """ The node immediately following the invocant in their parent's children list. If the invocant does not have a next sibling, it is None """

        if self.parent is None:
            return None

        # Can't use index(); we need to test by identity
        for i, child in enumerate(self.parent.children):
            if child is self:
                try:
                    return self.parent.children[i+1]
                except IndexError:
                    return None