void validate() {
            for (int i = 0; i < labels.length; i++)
                if (labels[i].isEqualTo(LabelCache.INVALID_INDEX_LABEL))
                    throw new IllegalArgumentException("Missing a label for dimension '" +
                                                       type.dimensions().get(i).name() + "' for " + type);
        }
Returns the type of the tensor this address is being built for.
vespajlib/src/main/java/com/yahoo/tensor/TensorAddress.java