public static Builder of(TensorType type) {
            //TODO Wire in expected map size to avoid expensive resize
            if (type.hasIndexedUnboundDimensions()) {
                return new UnboundBuilder(type, INITIAL_HASH_CAPACITY);
            } else {
                return new BoundBuilder(type, INITIAL_HASH_CAPACITY);
            }
        }
Create a builder depending upon the type of indexed dimensions.
If at least one indexed dimension is unbound, we create
a temporary structure while finding dimension bounds.
vespajlib/src/main/java/com/yahoo/tensor/MixedTensor.java