Generate CodeNodes for target address, registers node for function to
        function manager as return site

        :param int addr: target address
        :param int function_addr: address of function
        :return: None

def _function_add_return_site(self, addr, function_addr):
        """
        Generate CodeNodes for target address, registers node for function to
        function manager as return site

        :param int addr: target address
        :param int function_addr: address of function
        :return: None
        """
        try:
            target = self._to_snippet(self._nodes[addr])
        except KeyError:
            target = addr

        self.kb.functions._add_return_from(function_addr, target)