anchor.diff:              'projects/$projectid/traces/${traceHeader.split('/')[0]}';
   
           String createLogEntry(
  +          String message,
  +          LogSeverity severity, {
  +          Frame stackFrame,
  +        }) {
  +          // https://cloud.google.com/logging/docs/agent/configuration#special-fields
  +          final logContent = {
  +            'message': message,
  +            'severity': severity,
  +            // 'logging.googleapis.com/labels': { }
  +            if (traceHeader != null)
  +              'logging.googleapis.com/trace': traceValue(),
  +            if (stackFrame != null)
  +              'logging.googleapis.com/sourceLocation':
  +                  _sourceLocation(stackFrame),
  +          };
  +          return jsonEncode(logContent);
  +        }
  +
  +        String createErrorLogEntry(
             Object error,
             StackTrace stackTrace,
             LogSeverity logSeverity, {
  
positive.code:                       // functions_framework
                        predicate: (f) => f.package == 'shelf',
                      )
                    : createLogEntry(
                        error,
                        stackTrace,
                        LogSeverity.error,
  
negative.code: 
            final stackFrame = _frameFromChain(chain);
  
            return createLogEntry(
              '$error\n$chain'.trim(),
              logSeverity,
              stackFrame: stackFrame,
            );
          }
  
          final completer = Completer<Response>.sync();
  