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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 sibling(self, offs=1):
        '''
        Return sibling node by relative offset from self.
        '''
        indx = self.pindex + offs

        if indx < 0:
            return None

        if indx >= len(self.parent.kids):
            return None

        return self.parent.kids[indx]