assert fieldName == "input" || fieldName == "output";
assert fieldName == "inputChannel" || fieldName == "outputChannel";
    void setIOField (String fieldName, int fieldIndex, Channel newChannel)    {        assert fieldName == "input" || fieldName == "output";        Channel fieldsInstance [];        try            {                Class thisClass = this.getClass ();                assert thisClass != null;                Field ioField;                ioField  = thisClass.getField (fieldName);                if (ioField.getType () == newChannel.getClass ())                    {                        assert fieldIndex == 0;                        ioField.set (this, newChannel);                    } else {                        fieldsInstance = (Channel []) ioField.get (this);                        assert fieldsInstance != null;                        assert fieldsInstance.length > fieldIndex;                        fieldsInstance [fieldIndex] = newChannel;                    }            }        catch (Throwable error)            {                // this is all the other errors:                assert false : error.toString ();            }    }