code: def PlaceVOffsetT(self, x):
          
          N.enforce_number(x, N.VOffsetTFlags)
          self.head = self.head - N.VOffsetTFlags.bytewidth
          encode.Write(packer.voffset, self.Bytes, self.Head(), x)
docs: PlaceVOffsetT prepends a VOffsetT to the Builder, without checking
          for space.