public List<TensorFunction<NAMETYPE>> cellGeneratorFunctions() {
            var result = new ArrayList<TensorFunction<NAMETYPE>>();
            for (var fun : cells) {
                fun.asTensorFunction().ifPresent(result::add);
            }
            return result;
        }
Creates a dynamic tensor function for a bound, indexed tensor
vespajlib/src/main/java/com/yahoo/tensor/functions/DynamicTensor.java