Disabled triangle(icon) in single rows treetable

Hi, friends, someone knows, how i can remove or change te icon in a sinlge rows in a treetable I try with this

/* The closed triangle / .v-treetable-node-closed { background-image: url(path/to/your/image); }
/
The open triangle */ .v-treetable-node-open { background-image: url(path/to/your/image); }

but it does not work and i try with this too

I put this in code
ttable.setCellStyleGenerator(new Table.CellStyleGenerator() {
public String getStyle(Object itemId, Object propertyId) {
if (ttable.containsId(itemId) && propertyId == null) {
return “checkmark”;
}
return null;
}
});

and this in style :

.v-table-row-checkmark .v-treetable-node-closed {
background-image: url(info.png);

But It doesn’t not work, (Si alguien tiene informacion y pudiera contestar en español les agradeceria mucho, lo que quiero es desaparecer el triangulo que es el icono de expancion de las filas que no tienen hijos !! Gracias )