public GroupingOperation addOutputs(List<GroupingExpression> lst) {
        for (GroupingExpression exp : lst) {
            addOutput(exp);
        }
        return this;
    }
Convenience method to call {@link #addOutput(GroupingExpression)} for each element in the given list.

@param lst the list of expressions to add
@return this, to allow chaining
container-search/src/main/java/com/yahoo/search/grouping/request/GroupingOperation.java