public void visit(LogicNode node) {
        if (state != null) {
            throw new IllegalArgumentException("Logic expressions not supported in now expressions");
        }
        for (LogicNode.NodeItem item : node.getItems()) {
            item.getNode().accept(this);
        }
    }
Class which converts a selection tree into a set of queries per document type.
If unsupported operations are or illegal arguments are encountered, an exception is thrown.

@author Ulf Lilleengen
document/src/main/java/com/yahoo/document/select/convert/SelectionExpressionConverter.java