Returns the public object or None if there is no such element
        @return: the public object
        @rtype: L{Cpublic}

def get_public(self):
        '''
        Returns the public object or None if there is no such element
        @return: the public object
        @rtype: L{Cpublic}
        '''
        node = self.node.find('public')
        if node is not None:
            return Cpublic(node=node)
        else:
            return None