public Label objectLabel(String dimensionName) {
        for (int i = 0; i < dimensionNames.length; i++)
            if (dimensionNames[i].equals(dimensionName))
                return labels[i];
        
        return LabelCache.INVALID_INDEX_LABEL;
    }
Returns the label object of this dimension, or -1 if no label is specified for it
vespajlib/src/main/java/com/yahoo/tensor/PartialAddress.java