static private int computeDSS(List<TensorType.Dimension> dimensions) {
            long denseSubspaceSize = 1;
            for (var dimension : dimensions) {
                denseSubspaceSize *= dimension.size()
                        .orElseThrow(() -> new IllegalArgumentException("Unknown size of indexed dimension"));
            }
            return (int) denseSubspaceSize;
        }
An immutable index into a list of cells.
Contains additional information required
for handling mixed tensor addresses.
Assumes indexed dimensions are bound.
vespajlib/src/main/java/com/yahoo/tensor/MixedTensor.java