docs: public byte[] getUpdateChannelConfigurationSignature(UpdateChannelConfiguration updateChannelConfiguration, User signer) throws InvalidArgumentException {
  
          userContextCheck(signer);
  
          if (null == updateChannelConfiguration) {
  
              throw new InvalidArgumentException("channelConfiguration is null");
  
          }
  
          try {
  
              TransactionContext transactionContext = getTransactionContext(signer);
  
              final ByteString configUpdate = ByteString.copyFrom(updateChannelConfiguration.getUpdateChannelConfigurationAsBytes());
  
              ByteString sigHeaderByteString = getSignatureHeaderAsByteString(signer, transactionContext);
  
              ByteString signatureByteSting = transactionContext.signByteStrings(new User[] {signer},
                      sigHeaderByteString, configUpdate)[0];
  
              return ConfigSignature.newBuilder()
                      .setSignatureHeader(sigHeaderByteString)
                      .setSignature(signatureByteSting)
                      .build().toByteArray();
  
          } catch (Exception e) {
  
              throw new InvalidArgumentException(e);
          } finally {
              logger.debug("finally done");
          }
      }