code: def create(self, senderKeyName):
          
          try:
              senderKeyRecord = self.senderKeyStore.loadSenderKey(senderKeyName);
  
              if senderKeyRecord.isEmpty() :
                  senderKeyRecord.setSenderKeyState(KeyHelper.generateSenderKeyId(),
                                                  0,
                                                  KeyHelper.generateSenderKey(),
                                                  KeyHelper.generateSenderSigningKey());
                  self.senderKeyStore.storeSenderKey(senderKeyName, senderKeyRecord);
  
              state = senderKeyRecord.getSenderKeyState();
  
              return SenderKeyDistributionMessage(state.getKeyId(),
                                                  state.getSenderChainKey().getIteration(),
                                                  state.getSenderChainKey().getSeed(),
                                                  state.getSigningKeyPublic());
          except (InvalidKeyException, InvalidKeyIdException) as e:
              raise AssertionError(e)
docs: :type senderKeyName: SenderKeyName