How to use the delve.writers.CompositWriter function in delve

def _get_writer(self, save_to, writers_args) -> \
            delve.writers.AbstractWriter:
        """Create a writer to log history to `writer_dir`."""
        if issubclass(type(save_to), delve.writers.AbstractWriter):
            return save_to
        if isinstance(save_to, list):
            all_writers = []
            for saver in save_to:
                all_writers.append(self._get_writer(save_to=saver,
                                                    writers_args=writers_args))
            return CompositWriter(all_writers)
        if hasattr(delve, save_to):
            writer = getattr(delve, save_to)(**writers_args)
        else:
            raise ValueError('Illegal argument for save_to "{}"'.
                             format(save_to))
        return writer

def _warn_if_covariance_not_saveable(self, stats: List[str]):
        warn = False
        if 'cov' in stats:
            if isinstance(self.writer, CompositWriter):
                for writer in self.writer.writers:
                    if isinstance(writer, NPYWriter):
                        return
                warn = True
            elif not isinstance(self.writer, NPYWriter):
                warn = True
        if warn:
            warnings.warn("'cov' was selected as stat, but 'npy' (NPYWriter)"
                          "is not used as a save strategy, which is the only"

def __init__(self, writers: List[AbstractWriter]):
        """
        This writer combines multiple writers.
        :param writers: List of writers. Each writer is called when the CompositeWriter is invoked.
        """
        super(CompositWriter, self).__init__()
        self.writers = writers