public GroupingExpression getArg(int i) {
        return args.get(i);
    }
Returns the argument at the given index.

@param i The index of the argument to return.
@return The argument at the given index.
@throws IndexOutOfBoundsException If the index is out of range.
container-search/src/main/java/com/yahoo/search/grouping/request/FunctionNode.java