private boolean hasSingleUndividableChild(EmbracedNode node) {
        if (node.children().size() > 1) return false;
        if (node.children().get(0) instanceof OperationNode) return false;
        return true;
    }
Performs simple algebraic simplification of expressions

@author bratseth
searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/transform/Simplifier.java