overload of pandas.DataFrame.to_csv() to account
        for parameter transformation so that the saved
        ParameterEnsemble csv is not in Log10 space

        Parameters
        ----------
        *args : list
            positional arguments to pass to pandas.DataFrame.to_csv()
        **kwrags : dict
            keyword arguments to pass to pandas.DataFrame.to_csv()

        Note
        ----
        this function back-transforms inplace with respect to
        log10 before writing

def to_csv(self,*args,**kwargs):
        """overload of pandas.DataFrame.to_csv() to account
        for parameter transformation so that the saved
        ParameterEnsemble csv is not in Log10 space

        Parameters
        ----------
        *args : list
            positional arguments to pass to pandas.DataFrame.to_csv()
        **kwrags : dict
            keyword arguments to pass to pandas.DataFrame.to_csv()

        Note
        ----
        this function back-transforms inplace with respect to
        log10 before writing

        """
        retrans = False
        if self.istransformed:
            self._back_transform(inplace=True)
            retrans = True
        if self.isnull().values.any():
            warnings.warn("NaN in par ensemble",PyemuWarning)
        super(ParameterEnsemble,self).to_csv(*args,**kwargs)
        if retrans:
            self._transform(inplace=True)