Adds a tlink to the temporalRelations layer
        @type my_tlink: L{Ctlink}
        @param my_tlink: tlink object

def add_tlink(self,my_tlink):
        """
        Adds a tlink to the temporalRelations layer
        @type my_tlink: L{Ctlink}
        @param my_tlink: tlink object
        """
        if self.temporalRelations_layer is None:
            self.temporalRelations_layer = CtemporalRelations()
            self.root.append(self.temporalRelations_layer.get_node())
        self.temporalRelations_layer.add_tlink(my_tlink)