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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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)