overload of pandas.DataFrame.dropna()

        Parameters
        ----------
        *args : list
            positional args to pass to pandas.DataFrame.dropna()
        **kwargs : dict
            keyword args to pass to pandas.DataFrame.dropna()

        Returns
        -------
        Ensemble : Ensemble

def dropna(self, *args, **kwargs):
        """overload of pandas.DataFrame.dropna()

        Parameters
        ----------
        *args : list
            positional args to pass to pandas.DataFrame.dropna()
        **kwargs : dict
            keyword args to pass to pandas.DataFrame.dropna()

        Returns
        -------
        Ensemble : Ensemble

        """
        df = super(Ensemble, self).dropna(*args, **kwargs)
        if df is not None:
            pe = ParameterEnsemble.from_dataframe(df=df,pst=self.pst)
            pe.__istransformed = self.istransformed
            return pe