private static int[] createIndexesToReduce(TensorType tensorType, List<String> dimensions) {
        int[] indexesToReduce = new int[dimensions.size()];
        for (int i = 0; i < dimensions.size(); i++) {
            indexesToReduce[i] = tensorType.indexOfDimension(dimensions.get(i)).get();
        }
        return indexesToReduce;
    }
Creates a reduce function.

@param argument the tensor to reduce
@param aggregator the aggregator function to use
@param dimensions the list of dimensions to remove. If an empty list is given, all dimensions are reduced,
                  producing a dimensionless tensor (a scalar).
@throws IllegalArgumentException if any of the tensor dimensions are not present in the input tensor
vespajlib/src/main/java/com/yahoo/tensor/functions/Reduce.java