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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 decrypt(self, token, signature=None):
 """ Decrypt binary data. **中文文档** - 接收消息时只需要自己的privkey - 如需使用签名, 则双方都需要持有对方的pubkey """

        binary = rsa.decrypt(token, self.my_privkey)
        if signature:
            rsa.verify(binary, signature, self.his_pubkey)
        return binary