private String rpcWsAuthenticationCredentialsFile(final CommandLine commandLine) {
    final String filename = rpcWsAuthenticationCredentialsFile;

    if (filename != null) {
      RpcAuthFileValidator.validate(commandLine, filename, "WS");
    }
    return filename;
  }
Validates the authentication credentials file for the WebSocket.

@param commandLine CommandLine instance
@return Filename of the authentication credentials file
app/src/main/java/org/hyperledger/besu/cli/options/RpcWebsocketOptions.java