Returns the term identifier
        @rtype: string
        @return: the term identifier

def get_id(self):
        """
        Returns the term identifier
        @rtype: string
        @return: the term identifier
        """
        if self.type == 'NAF':
            return self.node.get('id')
        elif self.type == 'KAF':
            return self.node.get('mid')