code: def log(self, level, message, exc_info=None, reference=None):
          # pylint: disable=W0212
          
          if not isinstance(reference, pelix.framework.ServiceReference):
              # Ensure we have a clean Service Reference
              reference = None
  
          if exc_info is not None:
              # Format the exception to avoid memory leaks
              try:
                  exception_str = "\n".join(traceback.format_exception(*exc_info))
              except (TypeError, ValueError, AttributeError):
                  exception_str = "<Invalid exc_info>"
          else:
              exception_str = None
  
          # Store the LogEntry
          entry = LogEntry(
              level, message, exception_str, self.__bundle, reference
          )
          self.__reader._store_entry(entry)
docs: Logs a message, possibly with an exception
  
          :param level: Severity of the message (Python logging level)
          :param message: Human readable message
          :param exc_info: The exception context (sys.exc_info()), if any
          :param reference: The ServiceReference associated to the log