@Override
    public CompositeNode setChildren(List<ExpressionNode> newChildren) {
        if (newChildren.size() != 1)
            throw new IllegalArgumentException("Expected 1 child but got " + newChildren.size());
        return new UnpackBitsNode(newChildren.get(0), targetCellType, endian.toString());
    }
Macro that expands to the appropriate map_subspaces magic incantation

@author arnej
searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/UnpackBitsNode.java