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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_frame(self):
 """ Get a dataframe of metrics from this storage """

        metric_items = list(self.db.metrics.find({'run_name': self.model_config.run_name}).sort('epoch_idx'))
        if len(metric_items) == 0:
            return pd.DataFrame(columns=['run_name'])
        else:
            return pd.DataFrame(metric_items).drop(['_id', 'model_name'], axis=1).set_index('epoch_idx')