private Item buildDotProduct(String key, Inspector value) {
        HashMap<Integer, Inspector> children = childMap(value);
        String field = children.get(0).asString();
        Preconditions.checkArgument(children.size() == 2, "Expected 2 arguments, got %s.", children.size());
        return fillWeightedSet(value, children, new DotProductItem(field));
    }
Translates a list of grouping requests on JSON form to a list in the grouping language form
container-search/src/main/java/com/yahoo/search/query/SelectParser.java