code: def h2i(self, pkt, x):
          # type: (Optional[packet.Packet], int) -> int
          
          ret = super(UVarIntField, self).h2i(pkt, x)
          assert(not isinstance(ret, type(None)) and ret >= 0)
          return ret
docs: h2i 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 int: the converted value.
          @raise AssertionError