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)
        return type(self)(data=df,pst=self.pst)
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