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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 append_metrics(self, metrics, df_name):
 """Append new metrics to selected dataframes. Parameters metrics : metric.EvalMetric New metrics to be added. df_name : str Name of the dataframe to be modified. """

        dataframe = self._dataframes[df_name]
        _add_new_columns(dataframe, metrics)
        dataframe.loc[len(dataframe)] = metrics