code: def i2repr(self, pkt, x):
          # type: (Optional[packet.Packet], int) -> str
          
          return super(UVarIntField, self).i2repr(pkt, x)
docs: i2repr is overloaded to restrict the acceptable x values (not None)
  
          @param packet.Packet|None pkt: the packet instance containing this field instance; probably unused.  # noqa: E501
          @param int x: the value to convert.
          @return str: the converted value.