@Override
    public String toString(ToStringContext<NAMETYPE> context) {
        return "rename(" + argument.toString(context) + ", " +
                       toVectorString(fromDimensions, context) + ", " + toVectorString(toDimensions, context) + ")";
    }
If none of the dimensions change order after rename we can do a simple rename.
vespajlib/src/main/java/com/yahoo/tensor/functions/Rename.java