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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_default_metrics(config):
 """ Get the default metrics for a configuration. :param config: The configuration :type config: :class:`wily.config.WilyConfig` :return: Return the list of default metrics in this index :rtype: ``list`` of ``str`` """

    archivers = list_archivers(config)
    default_metrics = []

    for archiver in archivers:
        index = get_archiver_index(config, archiver)

        if len(index) == 0:
            logger.warning("No records found in the index, no metrics available")
            return []

        operators = index[0]["operators"]
        for operator in operators:
            o = resolve_operator(operator)
            if o.cls.default_metric_index is not None:
                metric = o.cls.metrics[o.cls.default_metric_index]
                default_metrics.append("{0}.{1}".format(o.cls.name, metric.name))
    return default_metrics