def callStore(self, nodeToAsk, key, value):   
        address = (nodeToAsk.ip, nodeToAsk.port)
        challenge = generate_challenge()
        try:
            private = OpenSSL.crypto.load_privatekey(OpenSSL.crypto.FILETYPE_PEM,
                                                    self.priv_key,
                                                    '')
            signature = OpenSSL.crypto.sign(private,
                                           nodeToAsk.id.encode("hex").upper() + challenge,
                                           "sha256")
        except:
            logger(self.sourceNode, "RETNONE: Signing of store failed")
            return None
        d = self.store(address,
                      self.sourceNode.id,
                      key,
                      value,
                      challenge,
                      signature)
        logger(self.sourceNode, "callStore initiated")
        return d.addCallback(self.handleSignedStoreResponse,
                            nodeToAsk,
                            challenge)
Registry.deregister: non-existant key returns False.
dataset/ETHPy150Open EricssonResearch/calvin-base/calvin/runtime/south/plugins/storage/twistedimpl/securedht/append_server.py/KademliaProtocolAppend.callStore--crossover with--dataset/ETHPy150Open xtrementl/focus/tests/unit/test_registry.py/TestRegistry.testNonExistKey__deregister