code: def to_csv(self,*args,**kwargs):
          
          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)
docs: 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