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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 PrependUOffsetTRelative(self, off):
 """Prepends an unsigned offset into vector data, relative to where it will be written. """


        # Ensure alignment is already done:
        self.Prep(N.UOffsetTFlags.bytewidth, 0)
        if not (off <= self.Offset()):
            msg = "flatbuffers: Offset arithmetic error."
            raise OffsetArithmeticError(msg)
        off2 = self.Offset() - off + N.UOffsetTFlags.bytewidth
        self.PlaceUOffsetT(off2)