static <NAMETYPE extends Name> String commaSeparatedNames(List<String> list, ToStringContext<NAMETYPE> context) {
        StringBuilder b = new StringBuilder();
        for (String element  : list)
            b.append(", ").append(context.resolveBinding(element));
        return b.toString();
    }
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