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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_parfiles(self,prefix):
 """ write the parameter ensemble to PEST-style parameter files Parameters prefix: str file prefix for par files Note ---- this function back-transforms inplace with respect to log10 before writing """

        if self.isnull().values.any():
            warnings.warn("NaN in par ensemble",PyemuWarning)
        if self.istransformed:
            self._back_transform(inplace=True)

        par_df = self.pst.parameter_data.loc[:,
                 ["parnme","parval1","scale","offset"]].copy()

        for real in self.index:
            par_file = "{0}{1}.par".format(prefix,real)
            par_df.loc[:,"parval1"] =self.loc[real,:]
            write_parfile(par_df,par_file)