def drop(self,arg):
        """ overload of pandas.DataFrame.drop()

        Parameters
        ----------
        arg : iterable
            argument to pass to pandas.DataFrame.drop()

        Returns
        -------
        Ensemble : Ensemble
        
        """
        df = super(Ensemble,self).drop(arg)
        return type(self)(data=df,pst=self.pst)
overload of pandas.DataFrame.drop()

        Parameters
        ----------
        arg : iterable
            argument to pass to pandas.DataFrame.drop()

        Returns
        -------
        Ensemble : Ensemble