def SystemFee(self):
        """
        Get the system fee.

        Returns:
            Fixed8:
        """
        if self.Version >= 1:
            return Fixed8.Zero()

        # if all outputs are NEO or gas, return 0
        all_neo_gas = True
        for output in self.outputs:
            if output.AssetId != GetSystemCoin().Hash and output.AssetId != GetSystemShare().Hash:
                all_neo_gas = False
        if all_neo_gas:
            return Fixed8.Zero()

        return super(IssueTransaction, self).SystemFee()