Adds a factuality to the factuality layer
        @type my_fact: L{Cfactuality}
        @param my_fact: factuality object

def add_factuality(self,my_fact):
        """
        Adds a factuality to the factuality layer
        @type my_fact: L{Cfactuality}
        @param my_fact: factuality object
        """
        if self.factuality_layer is None:
            self.factuality_layer = Cfactualities()
            self.root.append(self.factuality_layer.get_node())
        self.factuality_layer.add_factuality(my_fact)