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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 _to_file_format(self, iamc_index):
 """Return a dataframe suitable for writing to a file"""

        df = self.timeseries(iamc_index=iamc_index).reset_index()
        df = df.rename(columns={c: str(c).title() for c in df.columns})
        return df