PlaceSOffsetT prepends a SOffsetT to the Builder, without checking
        for space.

def PlaceSOffsetT(self, x):
        """PlaceSOffsetT prepends a SOffsetT to the Builder, without checking
        for space.
        """
        N.enforce_number(x, N.SOffsetTFlags)
        self.head = self.head - N.SOffsetTFlags.bytewidth
        encode.Write(packer.soffset, self.Bytes, self.Head(), x)