'As we flatten the tree, we use UP, DOWN nodes to represent
the tree structure.  When debugging we need unique nodes
so instantiate new ones when uniqueNavigationNodes is true.'

def addNavigationNode(self, ttype):

    navNode = None
    if (ttype == DOWN):
        if self.hasUniqueNavigationNodes():
            navNode = self.adaptor.createFromType(DOWN, 'DOWN')
        else:
            navNode = self.down
    elif self.hasUniqueNavigationNodes():
        navNode = self.adaptor.createFromType(UP, 'UP')
    else:
        navNode = self.up
    self.nodes.append(navNode)
