public static String asString(List<GroupingExpression> lst) {
        StringBuilder ret = new StringBuilder();
        for (int i = 0, len = lst.size(); i < len; ++i) {
            ret.append(lst.get(i));
            if (i < len - 1) {
                ret.append(", ");
            }
        }
        return ret.toString();
    }
Returns a string description of the given list of expressions. This is a comma-separated list of the expressions
own {@link GroupingExpression#toString()} output.

@param lst The list of expressions to output.
@return The string description.
container-search/src/main/java/com/yahoo/search/grouping/request/GroupingExpression.java