@Override
    public String toString() {
        return "<"
            + ((leftValue != null) ? "left," + leftValue : "right," + rightValue)
            + ">";
    }
Create a new {@link LeftOrRightValue} instance with the V2 value as {@code rightValue} and
V1 value as null.

@param rightValue the right V2 value
@param <V2>       the type of the value
@return a new {@link LeftOrRightValue} instance
streams/src/main/java/org/apache/kafka/streams/state/internals/LeftOrRightValue.java