code: def _add(self, other):
          
          if isinstance(other, self.__class__):
              sum_ = self._ip_dec + other._ip_dec
          elif isinstance(other, int):
              sum_ = self._ip_dec + other
          else:
              other = self.__class__(other)
              sum_ = self._ip_dec + other._ip_dec
          return sum_
docs: Sum two IP addresses.